Mycoplasma penetrans: Difference between revisions
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==Classification== | ==Classification== | ||
Latest revision as of 18:56, 19 August 2010
Classification
Higher order taxa
Bacteria; Firmicutes; Mollicutes; Mycoplasmatales; Mycoplasmataceae; Mycoplasma; Mycoplasma penetrans
Species
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NCBI: [1] |
Mycoplasma penetrans, Mycoplasma penetrans HF-2 strain
Description and significance
Mycoplasma penetrans looks like an elongated flask and has a tip-like structure at one pole of the cell which helps it penetrate into the eukaryotic cell (3). Mycoplasma penetrans are parasitic bacteria and inhabit humans specifically in the urogenital and respiratory tracts (1). Because the Mycoplasma penetrans genome sequence, ~1.3Mb, is larger than those of Mycoplasma pneumoniae, Mycoplasma genitalium, Mycoplasma pulmonis and Ureaplasma urealyticum, which range from 0.57 to 0.95 Mb, it is important to have its genome sequenced because this contrast suggests that this organism may possess additional genetic information involved in its unique infection process (1). Mycoplasma penetrans was first isolated was from a urine sample from a human immunodeficiency virus (HIV)-infected patient (2). In addition, Mycoplasma penetrans was also isolated from a patient with a case of primary antiphospholipid syndrome and not infected with HIV (3). This suggests that Mycoplasma penetrans can be pathogenic to humans without HIV (3).
Genome structure
Shotgun sequencing was used to sequence this organism. The genome size of Mycoplasma penetrans HF-2 strain was sequenced to be approximately 1,358,633 bp (3). Mycoplasma penetrans has a single circular chromosome which contains 1038 predicted coding sequences (CDSs) (3). Within the 1038 CDSs, 463 are specific to Mycoplasma penetrans (3). Mycoplasma penetrans have the minimum range of genome sizes that are necessary for self-replication (4). In general, Mycoplasmas are the simplest self-replicating bacteria (3). Mycoplasma penetrans has a very low average G + C content at 25.7% (1).
Cell structure and metabolism
Mycoplasmas penetrans, like the other Mycoplasma species, do not have a cell wall or an outer membrane (4,5). They also do not have most of the necessary genes for nutrient metabolism and thus adopt a lifestyle of a parasitic nature in host organisms (4). They have an elongated flask-like structure with a tip-like structure at one pole of the cell which may be what allows the mycoplasma to adhere to and invade the host cells (5).
Mycoplasma penetrans lacks uridine kinase, which is an essential cellular gene that is involved in pyrimidine metabolism (1). The phosphotransferase, uridine kinase, mediates phosphorylation of uridine and cytidine to make uridine and cytidine monophosphate (UMP/CMP) (1). In addition to uridine kinase, Mycoplasma penetrans also lacks the 5'-nucleotidase that metabolizes UMP and CMP to uridine and cytidine (1). Mycoplasma penetrans contains the uracil phosphoribosyltransferase (Upp) genethat is used to convert uracil to UMP, thus this Upp-dependent uracil conversion might be the main pathway for the production of UMP in the Mycoplasma penetrans (1). Mycoplasma penetrans also has another pathway that converts carbamoyl-phosphate to UMP via orotate-related metabolism (1).
Mycoplasma penetrans has a set of genes that code for enzymes which are involved in orotate-related metabolism (1). These include: aspartate carbamoyltransferase, dihydroorotase, dihydoorotate oxidase, orotate phosphoribosyltransferase, orotidine-5'-phosphate decarboxylase, and the pyrimidine operon regulatory protein (1). Orotate-related metabolism is related to an ATP synthesis system called the arginine dihydrolase pathway (1). The enzymes that participate in this pathway include: arginine deaminase, ornithine carbomoyltransferase, and carbamate kinase (1). Mycoplasma penetrans is the only species of Mycoplasmataceae to have a orotate-related metabolism that is related to the arginine dihydrolase pathway and pyrimidine metabolism (1).
Ecology
All species of Mycoplasmataceae are parasites by necessity and have very strict host specificity (3). Some of the hosts that Mycoplasmas in general have are humans, rodents, artiodactyla, perissodactyla and birds (1). Mycoplasmas will infect the host with a persistent nature and like many other parasites, they display antigenic diversity (1). This antigenic variation acts as a strategy for defending against immune responses by the host (1). Mycoplasma penetrans in particular is an intracellular bacterial pathogen (1). Thus its interaction with humans is of a parasitic sort. So far, studies have shown that Mycoplasma penetrans have only interacted and have been found in humans. Mycoplasma penetrans will infect human beings in the urogenital and respiratory tracts by means of penetrations, thus the name Mycoplasma penetrans (1).
Pathology
So far found only in humans, Mycoplasma penetrans is an intracellular bacterial pathogen (1). It typically penetrates into human cells and infects humans in the urogenital and respiratory tracts (1). The main virulence factor that Mycoplasma penetrans has is in its structure. It attaches to the host’s epithelial cells with its tip structure, the attachment organelle (1). After it attaches to the host cells, it penetrates through it, hence its name.
Because Mycoplasmas are parasitic, they will continue to colonize the host even with the presence of a specific immune response (4). The mechanisms under which Mycoplasms are able to evade the host immune responses are not yet clearly understood (4). But research has shown that the Mycoplasma species can modify their surface antigenic molecules at high frequency, which may assist in circumventing the host immune system (4).
Mycoplasma penetrans is particularly associated with HIV-1 infection, however, since it has also been isolated from a non HIV infected patient that had a case of primary antiphospholipid syndrome, Mycoplasma penetrans can indeed be pathogenic for humans without HIV (4).
Studies have shown that there is a link between Mycoplasma penetrans and HIV infection, implying that Mycoplasma penetrans could deteriorate the immune system in HIV infection as it acts as a cofactor in the progression of the HIV disease (5). However, it is still unclear and unproven whether or not Mycoplasma penetrans is a real cause of HIV accelerating or if it was only persistent in patients who were particularly immunocompromised (5).
Symptoms of Mycoplasma penetrans infection are typically dependent upon the symptoms of the HIV disease. In addition, it is believed that Mycoplasma penetrans contributes to the deterioration of the immune system during HIV disease. The areas that Mycoplasma penetrans affect are the urogenital and respiratory tracts (1). It is also believed that Mycoplasma penetrans is a primary cause of some forms of human urethritis and respiratory disease in people who do not have HIV (1).
Application to Biotechnology
This organism doesn’t seem to produce any useful compounds or enzymes. As of yet, it doesn’t seem as if Mycoplasma penetrans have much application to biotechnology. Mycoplasma penetrans is a parasitic organism and relies on its host.
Current Research
In 2003, Tarshis et al. researched the intracellular location and survival of Mycoplasma penetrans in HeLa cells (6). Using an acidotropic dye LysoTracker, the intracellular distribution of Mycoplasma penetrans within HeLa cells was investigated (6). This dye permeates the cell membranes and stays trapped in acidic compartments. When a pathogen binds to the host’s cell surface and internalizes, this is known as pathogen invasion (6). This research experiment attempts to see the intracellular fate of the invading Mycoplasma penetrans (6). Rabbit anti-Mycoplasma penetrans antibodies and red CY5 goat anti-rabbit IgG will be studied by the green LysoTracker by means of measuring the excitation and emission spectra (6). These images ran through a confocal laser scanning microscopy that showed that almost all of the Cy5 fluorescent foci in the infected HeLa cells were in intracellular compartments in the endosomes (6). The Mycoplasma penetrans had an antioxidant activity that was detected within the endosomes (6). Although the intracellular environment of the internalized Mycoplasma penetrans is still unknown, it is suggested that the endosomes that contained Mycoplasma penetrans fuse with lysosomes which are degradative in the routes of animal cells (6).
In 2002, Sasaki et al. completed the sequencing of the entire genome of Mycoplasma penetrans HF-2 strain (1). The genome of HF-2 consisted of 1,358,633 bp which contained 1038 CDSs with 1 set of rRNA genes and 30 tRNA genes (1). The research project included a Mycoplasma penetrans HF-2 strain from a patient with primary Mycoplasma penetrans infection (1). This strain was isolated from the tracheal aspirate and was used for DNA sequencing (1). The DNA from the HF-2 strain was first manipulated by cultivating it in a PPLO broth with heat-inactivated horse serum and glucose and penicillin (1). Then the Mycoplasma cells were lysed and incubated for 2 hours in a lysis buffer at 50 degrees Celsius (1). Then the lysate was extracted with phenol-choloroform. Next the DNA was precipitated with ethanol and then treated with RNaseA and later purified through extraction and precipitation (1). Next the DNA is shotgun sequenced and then the data is assembled and ran through a finishing software. The CDSs are then identified, annotated, and analyzed (1). The results of this research project gave general features of the Mycoplasma penetrans genome as well as ways of comparing the proteome of Mycoplasma penetrans and other species (1). It was also found that Mycoplasma penetrans did not have uridine kinase or the 5'-nucleotidase (1). This research also found many paralogous gene families in Mycoplasma penetrans with the largest being the p35 gene family, which is responsible for antigenic variation of lipoproteins. Much of the information discovered from this research will contribute to the general understanding of Mycoplasma penetrans and their infection of humans (1).
In 2002, Harino et al. investigated the surface antigenic variation in Mycoplasma penetrans (4). Mycoplasma penetrans is known to be able to change its surface antigenicity (4). They have lipid-associated membrane proteins (LAMPs) that help them change frequently (4). The P35 lipoprotein is a major antigen in the human immune system during infection by Mycoplasma penetrans (4). This family of surface membrane lipoproteins will have an ON/OFF phase variation (4). These phase variations happen at the transcriptional level of mpl genes (4). This research project studies the molecular mechanisms of the surface antigen profile change that occur in Mycoplasma penetrans (4). The study was of the 46-kDa protein which is present in M. penetrans strain HF-2 but not in GTU strain (4). Analysis of the nucleotide sequencing revealed that the promoter which contained the 135bp DNA of this gene had an invertible element that acted as a switch for gene expression (4). Whole-genome sequence data was used to identify the mpl genes of Mycoplasma penetrans strain HF-2 (4). It was discovered that there are at least 38 mpl genes in the Mycoplasma penetrans HF-2 genome and most have invertible promoter-like sequences. This research helped generate a model for the generation of surface antigenic variation by the multiple inversions in promoters (4).
References
Edited by Ling Tsay, student of Rachel Larsen and Kit Pogliano
KMG
