https://microbewiki.kenyon.edu/api.php?action=feedcontributions&user=Myam&feedformat=atommicrobewiki - User contributions [en]2024-03-28T20:55:40ZUser contributionsMediaWiki 1.39.6https://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12488Mycoplasma genitalium2007-06-02T20:51:29Z<p>Myam: /* Current Research */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long. They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome.<sup>[1]</sup> <br />
<br />
"''M. genitalium'' is so far one out fifteen mycoplasma species of human origin." They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[1]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most past research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
Studies have also been done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
While the role of ''Mycoplasma genitalium'' in causing non-gonococcal urethritis in men is well known, more recent research has focused on its pathology in women. While its role in causing cervicitis has been known, it has only recently been linked to pelvic inflammation disease in women.<sup>[11]</sup> Its role in other urogenital tract infections in women is still being studied, as well as ''M. genitalium'' effects on fertility and pregnancy.<sup>[3]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12487Mycoplasma genitalium2007-06-02T20:49:26Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long. They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome.<sup>[1]</sup> <br />
<br />
"''M. genitalium'' is so far one out fifteen mycoplasma species of human origin." They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[1]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most past research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies have also been done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
While the role of ''Mycoplasma genitalium'' in causing non-gonococcal urethritis in men is well known, more recent research has focused on its pathology in women. While its role in causing cervicitis has been known, it has only recently been linked to pelvic inflammation disease in women.<sup>[11]</sup> Its role in other urogenital tract infections in women is still being studied, as well as ''M. genitalium'' effects on fertility and pregnancy.<sup>[3]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12486Mycoplasma genitalium2007-06-02T20:46:29Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long. They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome.<sup>[1]</sup> <br />
<br />
"''M. genitalium'' is so far one out fifteen mycoplasma species of human origin." They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most past research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies have also been done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
While the role of ''Mycoplasma genitalium'' in causing non-gonococcal urethritis in men is well known, more recent research has focused on its pathology in women. While its role in causing cervicitis has been known, it has only recently been linked to pelvic inflammation disease in women.<sup>[11]</sup> Its role in other urogenital tract infections in women is still being studied, as well as ''M. genitalium'' effects on fertility and pregnancy.<sup>[3]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12485Mycoplasma genitalium2007-06-02T20:45:38Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long. They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome.<sup>[1]</sup> <br />
<br />
"''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most past research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies have also been done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
While the role of ''Mycoplasma genitalium'' in causing non-gonococcal urethritis in men is well known, more recent research has focused on its pathology in women. While its role in causing cervicitis has been known, it has only recently been linked to pelvic inflammation disease in women.<sup>[11]</sup> Its role in other urogenital tract infections in women is still being studied, as well as ''M. genitalium'' effects on fertility and pregnancy.<sup>[3]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12484Mycoplasma genitalium2007-06-02T20:43:53Z<p>Myam: /* Current Research */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most past research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies have also been done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
While the role of ''Mycoplasma genitalium'' in causing non-gonococcal urethritis in men is well known, more recent research has focused on its pathology in women. While its role in causing cervicitis has been known, it has only recently been linked to pelvic inflammation disease in women.<sup>[11]</sup> Its role in other urogenital tract infections in women is still being studied, as well as ''M. genitalium'' effects on fertility and pregnancy.<sup>[3]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=12483Mycoplasma genitalium2007-06-02T20:41:59Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies are also being done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (British Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' February 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11900Mycoplasma genitalium2007-05-30T22:37:52Z<p>Myam: /* Current Research */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most research on ''Mycoplasma genitalium'' has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on ''Mycoplasma genitalium'', tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”<sup>[2]</sup> <br />
<br />
By comparing ''Mycoplasma genitalium'' genome with ''Mycoplasma pneumonia'' and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in ''M. genitalium'' were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.<sup>[2]</sup><br />
<br />
Studies are also being done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, ''M. fermentans'' and ''M. penetrans'', have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”<sup>[9]</sup><br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11899Mycoplasma genitalium2007-05-30T22:36:13Z<p>Myam: /* Current Research */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Most research on Mycoplasma genitalium has focused on its minimal genome in order to determine the genes necessary for life. Experiments done in the Institute of Genomics Research on Mycoplasma genitalium, tried to determine the genes that are essential for a living organism. Their research could pave the way for the “creation of a living organism in the laboratory.”[2] <br />
<br />
By comparing Mycoplasma genitalium genome with Mycoplasma pneumonia and utilizing gene knockout techniques, scientists discovered that only 300 out of 517 genes were necessary for life. The functions of 111 of these genes in M. genitalium were unknown. It was found that genes for some tRNAs that were thought as essential, were not necessary. The genes that are defined as essential in their work only apply under laboratory conditions and not in the natural environment. Their work also has a lot of ethical and environmental implications as it involves creating new life.[2]<br />
<br />
Studies are also being done on the association of mycoplasmas and AIDS, specifically their role in AIDS activation. Their ability as possible factors in AIDS activation has increased research into mycoplasma and their pathogenesis. “The substantial number of studies carried out on the AIDS-associated mycoplasmas, M. fermentans and M. penetrans, have considerably advanced our knowledge of mycoplasma cell biology and host immune system modulation…however, thus far the proposed role of mycoplasmas in AIDS activation remains controversial and doubtful.”[9]<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11892Mycoplasma genitalium2007-05-30T21:43:48Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11891Mycoplasma genitalium2007-05-30T21:41:33Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli''.<sup>[9]</sup> There is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[1]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts." It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11889Mycoplasma genitalium2007-05-30T21:20:19Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts." It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that ''M. genitalium'' can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11888Mycoplasma genitalium2007-05-30T21:19:30Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts." It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11887Mycoplasma genitalium2007-05-30T21:18:43Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, ''M. genitalium'' is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11886Mycoplasma genitalium2007-05-30T21:17:32Z<p>Myam: /* Cell Structure and Metabolism */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' is flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids such as phospholipids, glycolipids, and neutral lipids, are located in the cell membrane. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11884Mycoplasma genitalium2007-05-30T21:14:01Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. "''M. genitalium'' is so far one out fifteen mycoplasma species of human origin."<sup>[3]</sup> They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11883Mycoplasma genitalium2007-05-30T21:12:43Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Without adhesion there can be no infection. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding a 114 kDa protein of unknown function. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and “to adapt to various cell surfaces.”<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11880Mycoplasma genitalium2007-05-30T20:56:46Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
AAdhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<sup>[3]</sup><br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11878Mycoplasma genitalium2007-05-30T20:56:17Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
AAdhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain proteins called adhesins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Multiple repeat fragments of both these genes are found throughout the genome and make up 4.7% of its total genome, a high cost considering its limited genome. Recombination of the MgPa operon with the repeat fragments may generate almost unlimited variation, allowing for the evasion of the host’s immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11437Mycoplasma genitalium2007-05-28T22:31:54Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
"Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts."<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11432Mycoplasma genitalium2007-05-28T22:13:06Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and possessing only a plasma membrane, M. genitalium is much more osmotically sensitive than other bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11430Mycoplasma genitalium2007-05-28T22:09:43Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that M. genitalium can enter host cells using their tip structure. Being able to exist as an intracellular pathogen may allow for protection against the host’s immune system, it could also explain the difficulties in fully eliminating the disease, despite antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11425Mycoplasma genitalium2007-05-28T21:58:10Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the Gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to Gram-positive bacteria.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from Gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11424Mycoplasma genitalium2007-05-28T21:52:37Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens causing mostly mild and chronic infections, but rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11147Mycoplasma genitalium2007-05-26T06:58:11Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592. <br />
<br />
3. Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.<br />
<br />
4. Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. Razin, S., Yogev, D., and Naot, Y. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11146Mycoplasma genitalium2007-05-26T06:53:25Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1.'' Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11145Mycoplasma genitalium2007-05-26T06:53:00Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” Danish Medical Bulletin – No. 1. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” ''Journal of the European Academy of Dermatology and Venereology.'' January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=11144Mycoplasma genitalium2007-05-26T06:50:46Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” "Journal of the European Academy of Dermatology and Venereology." January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' December 1998. Volume 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by Michael Yam, student of Rachel Larsen and Kit Pogliano</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10894Mycoplasma genitalium2007-05-17T07:10:43Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been discovered in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first found in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10893Mycoplasma genitalium2007-05-17T07:05:08Z<p>Myam: </p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10892Mycoplasma genitalium2007-05-17T07:04:40Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be the most effective form of treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10867Mycoplasma genitalium2007-05-15T22:22:23Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10866Mycoplasma genitalium2007-05-15T22:21:41Z<p>Myam: /* References */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
1. C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
2. [http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
3. [http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
4. [http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
5. Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
6. Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
7. Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
8. [http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
9. Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
10. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
11. Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10865Mycoplasma genitalium2007-05-15T22:20:12Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation, allowing for the evasion of the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''.<sup>[4]</sup> Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10864Mycoplasma genitalium2007-05-15T22:14:26Z<p>Myam: /* Pathology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<sup>[3]</sup><br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis.<sup>[3]</sup> <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces.<sup>[3]</sup> Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<sup>[3]</sup><br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<sup>[4]</sup><br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10863Mycoplasma genitalium2007-05-15T22:12:58Z<p>Myam: /* Cell Structure and Metabolism */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.<sup>[9]</sup><br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.<sup>[9]</sup><br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.<sup>[9]</sup> Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.<sup>[7]</sup> <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.<sup>[9]</sup><br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10862Mycoplasma genitalium2007-05-15T22:11:54Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.<sup>[9]</sup><br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.<sup>[9]</sup> <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.<sup>[9]</sup> <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.<sup>[10]</sup> In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.<sup>[1]</sup><br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.<sup>[9]</sup> They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.<sup>[10]</sup> They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.<sup>[9]</sup><br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.<sup>[1]</sup> <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.<sup>[1]</sup><br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10861Mycoplasma genitalium2007-05-15T22:10:17Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.<sup>[1]</sup> They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.<sup>[3]</sup> <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.<sup>[2]</sup><br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10860Mycoplasma genitalium2007-05-15T22:09:22Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>[9]</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>[9]</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>[3]</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>[9]</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10859Mycoplasma genitalium2007-05-15T22:08:49Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>9</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.<sup>9</sup><br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.<sup>3</sup> It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<sup>9</sup><br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10858Mycoplasma genitalium2007-05-15T22:08:10Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.<sup>9</sup> <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.[9]<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.[3] It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.[9]<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10857Mycoplasma genitalium2007-05-15T22:05:07Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.[9] <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.[9]<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.[3] It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.[9]<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10856Mycoplasma genitalium2007-05-15T22:04:50Z<p>Myam: /* Ecology */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well.[9] <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures minimal exposure to the external environment.99]<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts.[3] It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.[9]<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10855Mycoplasma genitalium2007-05-15T21:59:23Z<p>Myam: /* Cell Structure and Metabolism */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' are flask shaped and do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also present and strongly antigenic, and undergo size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the fatty acids provided from their host. There is a price for this gene saving. Being unable to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this by incorporating large amounts of cholesterol from their host into their membrane. Cholesterol serves as a an effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP, which is less efficient than oxidative phosphorylation. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. Despite these limited ATP producing systems, ''M. genitalium'' grow well in vivo due to the relatively small amounts of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10854Mycoplasma genitalium2007-05-15T21:35:07Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It is assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of nutrients from its host such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of adhesin proteins.[1] <br />
<br />
Due to its minimal set of genes needed for protein synthesis and DNA replication, protein synthesis and cell replication occur much slower compared to ''E. coli''. '' M. genitalium'' grow much more slowly with a generation time of about 24 hours.[1]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10853Mycoplasma genitalium2007-05-15T21:27:08Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study in the lab under in vitro conditions, due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10852Mycoplasma genitalium2007-05-15T21:23:55Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes such as those involved with cell wall synthesis and various biosynthetic pathways, as they adapted to a more parasitic lifestyle. This allows them to have some of the smallest genomes of any bacterial organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study under classical experimental methods due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10851Mycoplasma genitalium2007-05-15T21:17:44Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes involved in cell wall synthesis and biosynthetic systems as they adapted to a more parasitic lifestyle, as a result they have some of the smallest genomes of any self-replicating organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study under classical experimental methods due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10850Mycoplasma genitalium2007-05-15T21:16:45Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures for these functional RNAs.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes involved in cell wall synthesis and biosynthetic systems as they adapted to a more parasitic lifestyle, as a result they have some of the smallest genomes of any self-replicating organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study under classical experimental methods due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10849Mycoplasma genitalium2007-05-15T21:16:24Z<p>Myam: /* Genome structure */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from Gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram-positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures for these functional RNAs.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes involved in cell wall synthesis and biosynthetic systems as they adapted to a more parasitic lifestyle, as a result they have some of the smallest genomes of any self-replicating organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study under classical experimental methods due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myamhttps://microbewiki.kenyon.edu/index.php?title=Mycoplasma_genitalium&diff=10848Mycoplasma genitalium2007-05-15T21:10:26Z<p>Myam: /* Description and significance */</p>
<hr />
<div>{{Biorealm Genus}}<br />
<br />
==Classification==<br />
<br />
===Higher order taxa===<br />
<br />
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma<br />
<br />
===Genus=== <br />
<br />
<br />
''Mycoplasma genitalium''<br />
<br />
<br />
<br />
{|<br />
| height="10" bgcolor="#FFDF95" |<br />
'''NCBI: [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Tree&id=2&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy]'''<br />
|}<br />
<br />
==Description and significance==<br />
''Mycoplasma genitalium'' is a parasitic bacterium with the smallest known genome of any free living bacteria at 580,070 bp long.[1] They are believed to have evolved from Gram-positive bacteria through a process of degenerative evolution, leading to the loss of many ancestral genes and the reduction of its genome. ''M. genitalium'' is so far one out fifteen mycoplasma species of human origin. They are often found invading and adhering to the epithelial linings of the urogenital tracts, but they have also been isolated in the respiratory tract. ''M. genitalium'' is associated with many urogenital tract infections, in both men and women. In fact ''M. genitalium'' was first isolated in two men with non-gonococcal urethritis.[3] <br />
<br />
Besides its importance as a pathogen, its genome has been extensively studied in order to determine the minimal set of genes essential for life.[2]<br />
<br />
==Genome structure==<br />
In 1995, the entire genome of ''M. genitalium'' was sequenced in less than 6 months using the random shotgun sequencing technique. It was found to have the smallest known genome of any free-living organism at about 580 kilobase pairs long, with 479 coding sequences for proteins. For comparison [http://en.wikipedia.org/wiki/M._pneumoniae ''M. pneumoniae''] has 677 protein coding sequences, [http://en.wikipedia.org/wiki/Haemophilus_influenzae ''H. influenzae''] has 1703, and ''E. coli'' K-12 has 4,288.[9]<br />
<br />
The genome-sequencing projects have shown that there is a 62% similarity between the coding regions of ''Bacillus subtilis'' and a 56% similarity to ''E. coli'', however there is even closer similarity to the gram positive species of [http://microbewiki.kenyon.edu/index.php/Lactobacillus ''Lactobacillus''] and [http://microbewiki.kenyon.edu/index.php/Clostridium ''Clostridium'']. This provides strong evidence that the mycoplasmas are more closely related to gram-positive bacteria with low GC contents.[9] <br />
<br />
Low GC content is a characteristic of all mycoplasmas. ''M. genitalium'' possess an average GC content of 32%. Genes coding for rRNA average 44% and 52% for tRNA. The GC content for rRNA and tRNA are much higher than the rest of the genome due to the importance of their secondary structures for these functional RNAs.[9] <br />
<br />
The Mycoplasmas evolved through a process of degenerate evolution from gram-positive bacteria. They have lost many genes involved in cell wall synthesis and biosynthetic systems as they adapted to a more parasitic lifestyle, as a result they have some of the smallest genomes of any self-replicating organism.[10] In addition, their UGA codon is used as another codon for tryptophan instead of a stop codon found in other organisms.[1]<br />
<br />
''M. genitalium'' lack any genes for amino acid biosynthesis and contain few genes for nucleic acid, vitamins, and fatty acid biosynthesis. They must acquire these components from their host or through an artificial medium. This makes them difficult to study under classical experimental methods due to their strict growth requirements. They also lack genes for oxidative metabolism (Kreb cycle, or Entner-Doudoroff pathway), gluconeogenesis, catalase and peroxidase, or other toxic oxygen protective enzymes. They also appear to possess few regulatory proteins, such as two-component systems and no identifiable transcription factors.[9] They do however possess the genes necessary for DNA replication, transcription, and translation, but even these contain a minimal set of rRNA and tRNA genes.[10] They also contain genes for glycolysis, phospholipids metabolism, and for converting vitamins to cofactors. They have less DNA repair genes compared to ''E. coli'' and ''H. influenzae.'' It can be assumed however that the genes detected such as uracil DNA glycosylase, exinuclease ABC genes, and recA must be essential for proper DNA repair in all organisms.[9]<br />
<br />
While ''M. genitalium'' have been able to reduce its genome during the course of its evolution as a parasite, it must maintain genes necessary for this mode of life. A significant portion of its genome is devoted to the transport of exogenous nutrients such as glucose and fructose, as well as genes for attachment organelles, adhesins, and antigenic variation to evade the host immune system. In fact it’s estimated that 5% of its total DNA is devoted to repeat fragments used for antigenic recombination of cell pole adhesins.[1] <br />
<br />
''M. genitalium'' possess the minimum set of genes needed for protein synthesis and DNA replication, however as a result of this protein synthesis and cell replication occurs much slower compared to ''E. coli''. '' M. genitalium'' grow slowly with a generation time of 24 hours.[1]<br />
<br />
''E. coli'' and ''M. genitalium'' both have 12% of their genome occupied by intergenic non-coding regions such as control elements, promoters, and terminators. However, ''M, genitalium'' possess more operon systems, probably reducing the number of regulatory elements for the transcription of genes and further contributing to the reduction of its genome. This increases gene density with the average gene size for ''M. genitalium'' at 1,040 base pairs, compared with 900 in ''H. influenzae''.[9]<br />
<br />
==Cell Structure and Metabolism==<br />
''M. genitalium'' have a flask-like shape and they do not have a cell wall like all mycoplasma species. Lacking a cell wall they have only a plasma membrane, with over two thirds of its mass containing proteins and the rest being membrane lipids. Virtually all mycoplasma lipids are located in the cell membrane such as phospholipids, glycolipids, and neutral lipids. Membrane lipoproteins are also found to be much higher in mycoplasma species compared to other eubacteria membranes. In addition their membrane lipoproteins are strongly antigenic, many of which undergo antigenic and/or size variations.[9]<br />
<br />
They lack genes for synthesizing any fatty acid and therefore depend on their host for their supply. Most mycoplasmas generally synthesize their own membrane phospholipids and glycolipids from the exogenously provided fatty acids. There is a price for this gene saving. Being deficient in the ability to regulate membrane fluidity by controlling their fatty acid biosynthesis, the mycoplasmas overcome this difficulty by incorporating large quantities of cholesterol from their hosts into their membrane. Cholesterol serves as a very effective buffer of membrane fluidity.[9]<br />
<br />
''M. genitalium'' is a motile mycoplasma. It uses a specialized tip structure to attach to surfaces and glide across them. The average speed is about 0.1 μ/s, which is slower than that recorded for ''M. pneumoniae''. This tip structure also serves as the attachment organelle, allowing ''M. genitalium'' to adhere to eukaryotic cells.[9] Attachment is mediated mostly by the adhesin protein MgPa, which undergoes antigenic recombination.[7] <br />
<br />
As mentioned earlier,'' M. genitalium'' is deficient in many genes coding for components of many biosynthetic pathways, including energy metabolism. ''M. genitalium'' depend mostly on glycolysis for the production of ATP. Genes that encode the components of the pyruvate dehydrogenase complex, phosphotransacetylase, and acetate kinase were also detected, as well as an incomplete pentose phosphate pathway. Many energy-producing systems are lacking such as the TCA (tricarboxylic acid) cycle, and no quinones and cytochromes were found in any of the mycoplasmas. ATP is produced in mycoplasmas by subtrate-level phosphorylation, less efficient than oxidative phosphorylation. Despite these limited and inefficient ATP producing systems, ''M. genitalium'' grow well in vivo most likely due to the relatively small investment of ATP needed for their limited biosynthetic pathways.[9]<br />
<br />
==Ecology==<br />
Due to the scarcity of genes involved in biosynthetic pathways, mycoplasmas depend on a supply of nutrients from their hosts and as such they exist as parasites of various animals and plants. ''M. genitalium'' is found primarily in the urogenital tract of humans; however they have been isolated in the respiratory tract as well. <br />
<br />
Lacking a cell wall and limited only by their plasma membrane,'' M. genitalium'' is much more osmotically sensitive than walled bacteria. As a parasite in the human urogenital tract they can exist in an osmotically constant environment. Its transmission by sexual contact also ensures its minimal exposure to the external environment.<br />
<br />
Mycoplasmas are benign pathogens, causing mostly mild and chromic infections, rarely killing their hosts. It is possible that mycoplasmas, including ''M. genitalium'' are evolving towards symbiosis.<br />
<br />
==Pathology==<br />
The urogenital tract appears to be the primary tissue infected by ''M. genitalium'', however they have also been isolated in the respiratory tract. Tissue damage is only partially caused by toxins and harmful metabolites produced by ''M. genitalium'', such as hydrogen peroxide and super-oxide metabolites. Most likely the much of the damage is caused by the inflammatory response of the host immune system.<br />
<br />
In men, ''M. genitalium'' is a major agent in urogenital tract disease. In a range of studies they have been found in 10-45% of men with non-gonococcal urethritis. The role of ''M. genitalium'' in women is less understood, but they are believed to be able to cause cervicitis and pelvic inflammation disease (PID). Only incomplete evidence has been established for the role of M. genitalium on infertility, while its role in bacterial vaginosis (BV) and adverse pregnancy in women have not been fully determined. ''M. genitalium'' can be sexually transmitted with rates similar to ''Chlamydia trachomatis'', another pathogen which can cause urethritis. <br />
<br />
Adhesion of mycoplasmas to host cells is required for colonization and for infection. Loss of adhesion leads to a loss on infectivity. They attach to host cells using a specialized tip structure that contain adhesin proteins. The main adhesin protein is encoded by the MgPa gene, followed by a gene encoding an 114 kDa protein. Repeat fragments of both these genes, with 78-90% sequence similarity, are found throughout the genome and make up 4.7% of its total genomic content. A high cost considering its limited genome. Recombination of the MgPa operon with the MgPa-repeat fragments may generate almost unlimited variation in these epitopes, allowing unique opportunities to evade the immune response and to adapt to various cell surfaces. Other variable antigens are currently under study and may prove to offer additional variation for ''M. genitalium'', including the lipoproteins on the plasma membrane.<br />
<br />
There is also evidence that'' M. genitalium'' can enter host cells using their tip structure. It has been shown that ''M. genitalium'' on contact with human lung fibroblast, the plasma membrane of the cell appears to be forced inward, with membrane pockets resembling clathrin-coated pits. It is believed that the mycoplasma may be able to adhere to and enter cells by a receptor-mediated event similar to cell entry of chlamydias. Being able to exist as an intracellular pathogen could explain difficulties in fully eliminating the disease and preventing relapse, despite active antibiotic treatments.<br />
<br />
The macrolide antibiotic group appears to be more effective than the tetracyclines in treatment of ''M. genitalium''. Further research is still being done on proper treatment.<br />
<br />
==Application to Biotechnology==<br />
Does this organism produce any useful compounds or enzymes? What are they and how are they used?<br />
<br />
==Current Research==<br />
<br />
Enter summaries of the most recent research here--at least three required<br />
<br />
==References==<br />
C.M. Fraser et al. Science. 1995. Volume 270: 397-403<br />
<br />
[http://www.bmj.com/cgi/content/full/319/7225/1592/a Deborah, Josefson. “Scientists try to discover how many genes are necessary to build a living organism.” ''BMJ'' (Bristish Medical Journal). December 18, 1999. Volume 319(7225): 1592.] <br />
<br />
[http://www.danmedbul.dk/Dmb_2006/0106/0106-disputatser/DMB3770.htm Jensen, Jorgen Skov. “Mycoplasma genitalium infections” ''Danish Medical Bulletin – No. 1''. Fenruary 2006. Volume 53: 1-27.]<br />
<br />
[http://www.blackwell-synergy.com/doi/abs/10.1111/j.1468-3083.2004.00923.x Jensen, Jorgen Skov. “Mycoplasma genitalium: the aeticological agent of urethritis and other sexually transmitted diseases.” Journal of the European Academy of Dermatology and Venereology. January 2004. Volume 18(1): 1-11.]<br />
<br />
Maniloff, Jack. “The minimal cell genome: ‘On being the right size.’” ''Proceedings of the National Academy of Sciences of the United States of America.'' September 1996. Volume 93: 10004-10006.<br />
<br />
Morgan, Nacy A. “Microbial Minimalism: Genome Reduction in Bacterial Pathogens.” ''Cell''. March 8, 2002. Volume 108: 583-586.<br />
<br />
Peterson, Scott et al. “Characterization of repetitive DNA in the Mycoplasma genitalium genome: Possible role in the generation of antigenic variation.” ''Proceedings of the National Academy of Sciences of the United States of America''. December 1995. Volume 92: 11829-11833.<br />
<br />
[http://genomebiology.com/2001/2/2/comment/2002 Peterson, Scott and Claire M. Fraser. “The complexity of simplicity.” '' Genome Biology''. 2001. Volume 2(2). ] <br />
<br />
Razin, Shmuel. “The minimal cellular genome of mycoplasma.” ''Indian Journal of Biochemistry & Biophysics''. Feb-Apr 1997. Volume 34(1-2):124-30.<br />
<br />
[http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=9841667 Shmuel Razin, David Yogev, and Yehudith Naot. “Molecular Biology and Pathogenicity of Mycoplasmas.” '' Microbiology Molecular Biology Review.'' 1998 December; 62(4): 1094–1156.]<br />
<br />
Walsh, Nancy. “M. genitalium tied to pelvic inflammatory disease: sexual transmission – Gynecology.” OB/GYN News. Sept 15, 2003.<br />
<br />
<br />
Edited by student of Michael Yam</div>Myam