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[[Image:060718_gold_bacteria_01.jpg|thumb|300px|right|'' Bacterial induced formation of Cd crystals by Ralstonia metallidurans on Zirfon M5 membranes in the continuous tubular membrane reactor.''. [http://images.livescience.com/images/060718_gold_bacteria_01.jpg]]]




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''Ralstonia syzygii''<br/ >
''Ralstonia syzygii''<br/ >
''Ralstonia taiwanensis''<br/ >
''Ralstonia taiwanensis''<br/ >


==Description and significance==
==Description and significance==


<font size="+1"><font size="3">Alcaligenes eutrophus CH34 was just recently renamed ''Ralstonia metallidurans''. This species was first isolated in 1976 from the sludge of a zinc decantation tank in Belgium that was polluted with high concentrations of several heavy metals, it and other metal-resistant members of the genus Ralstonia are frequently found in sediments and soils with a high content of heavy metals from diverse ecological niches(2).
''Ralstonia metallidurans'' is a gram-negative microbe that does not form spores. It is unique in that it can fluorish in millimolar concentrations of heavy metals, such as gold, that are normally toxic to bacteria. According to discoverer Frank Reith, ''Ralstonia metallidurans'' "is able to survive in concentrations of gold that would kill most other micro-organisms" (1). Not only can these microbes withstand toxic concentrations of metals, they are found to be able to precipitate gold. Although it is unknown exactly how this process works, it is "possible that the microbe screens out gold as part of an effort to detoxify its immediate environment" (1).


''Ralstonia metallidurans'' is gram-negative, non-spore forming bacterium which thrives in the presence of millimolar concentrations of heavy-metals such as Zn, Cd, Co,Pb, Hg, Ni and Cr. Metal resistance functions are mainly encoded on two plasmids replicated in the bacterium, pMOL28 and pMOL30, which produce metal exporters that pump metal ions out of the cell. This process aids in protecting intracellular macromolecules from the toxic effects and damages of high concentrations of metal (2).
''Ralstonia metallidurans'' and other metal resistant microbes are often found in sediments with a high content of heavy metals from diverse geographical locations. The reference strain, CH34, was first discovered in 1976, from the sludge of a zinc decantation tank in Belgium that was polluted with high concentrations of several heavy metals. Frank Reith (and colleagues) at Australian National University further isolated and grew the bacteria in the lab.


The significance of this microbe lays in that its genome contains plasmids that confer resistance to heavy metals, such as Zinc, Mercury, Cadmium, Cobalt, etc.
In 1992, Kostman et al. developed a PCR-ribotyping method for B. cepacia which could detect significant polymorphisms in the intergenic 16S-23S spacer of rRNA genes (7). In 1997, Shreve et al. used PCR-RFLP analysis for the 16S and 23S regions of the rRNA genes in an epidemiological study of B. cepacia infection (21). Segonds et al. used PCR-RFLP analysis of the 16S rRNA gene to differentiate Burkholderia species (20).
==Genome structure==
The genome of ''R. metallidurans CH34'' has been extensively studied. It contains two large plasmids that encode for heavy metal resistance. pMOL28 (163 kb) furnishes tolerance to Nickel, Mercury, and Cobalt; pMOL30 (238 kb) confers resistance to Zinc, Cadmium, Mercury, and Cobalt (3). These plasmids are self-transmissible in homologous matings, but at low frequencies (3). The entire genome is approximately 6900 kb in size. In addition to the plasmids pMOL28 and pMOL30, it also contains two circular chromosomes (8). Furthermore, the genome encodes "8 P-type ATPase involved in metal efflux specialized in lead, cadmium, thallium and/or copper efflux, and several other mechanism involved in metal processing" (1). Together, these genetic elements contribute to the microbe's unique ability to survive in harsh environments.
The amplicons of R. paucula isolates were digested with AciI and AlwI. All of the strains shared a single pattern with each of the two endonucleases. The AciI pattern was composed of eight fragments (340, ~200, 122, 119, 92, 75, 49, and 44 bp), and the AlwI pattern was composed of four fragments (418, 218, 130, and 75 bp)
==Cell structure and metabolism==
''R. metallidurans'' is a gram-negative bacillus (rod shaped). Therefore, it has the structural features of gram-negative bacteria, such as cell walls containing peptidoglycan, an outer membrane containing LPS and porins, and a periplasmic space (2).


This bacteria is better able to withstand high concentrations of heavy metals than any other well-studied organism. It could potentially play an important role in the bioremediation of contaminated water sources. The survival in this extreme habitat and genomic sequencing suggest that it is one of the first life forms on earth, existing when there was very little oxygen in the atmosphere some 2.5 billion years ago.
''R. metallidurans'' is able to utilize a variety of substrates as its carbon source. It can grow autotrophically using molecular hydrogen as an energy source and carbon dioxide as its carbon source. Furthermore, in the presence of nitrate, it can grow anaerobically (6). When grown lithoautotrophically on molecular hydrogen, it forms cytoplasmic NAD-reducing and membrane bound hydrogenase. It does not grow on fructose (3) and its optimal growth temperature is 30 C (4).


==Genome structure==
==Ecology==
Due to its ability to withstand toxic metals, ''R. metallidurans'' has been studied to utilize this characteristic in areas of bioremediation (10). Furthermore, new findings of a lead binding protein isolated from ''R. metallidurans'' is key in preventing lead poisoning (11).


Its genome is approximately 6800 kb in size.  The strain CH34 carries two large circular plasmids (pMOL28=180 kbp and pMOL30=240 kbp) and two circular chromosomes, which consist  of a variety of genes that code for metal resistance and carrying gene clusters that encode cation-efflux machinery that spans the entire length of the membrane. The two critical plasmids are essential for it's existence, pMOL28 (163 kilobases) which specifies nickel, mercury, and cobalt resistance and pMOL30 (238 kilobases) specifying zinc, cadmium, mercury, and cobalt resistance.
==Pathology==
[[Image:Number1 1.png |frame|center|. Circular genome of plasmid 1 for Ralsontia metallidurans found using [tools.neb.com]]]
''R. metallidurans'' has not been found to be pathogenic to humans. However, a near relative, ''R. solancearum'', that shares some of the metal resistant genes, has been found to cause disease in plants (10).
R. paucula has been isolated from pool water, groundwater, and bottled mineral water (2, 9, 17) and from clinical specimens. Despite its low pathogenicity, it is now recognized as an opportunistic pathogen which can generate serious infections such as septicemia, peritonitis, abscess, and tenosynovitis, particularly in immunocompromised patients


The plasmids are self-transmissible in homologous matings, but at low frequencies. Experiments have been performed where plasmid-free cells of strain CH34 are still able to grow lithoautotrophically and to form both hydrogenases, indicating that the hydrogenase genes are located on the chromosome, in contrast to the Hox structural genes of strain H16, which are located on the megaplasmid pHG1 (450 kilobases). Interestingly, this genome also contains 8 P-type ATPase involved in metal efflux specialized in lead, cadmium, thallium and/or copper efflux, and several others mechanisms involved in metal processing.
==Application to Biotechnology==
''R. metallidurans'' has been found to produce enzymes that may be used in constructing a fuel cell (12). These enzymes are able to oxidize hydrogen, which can ultimately result in the production of electricity. Scientists are in the process of researching this phenomenom (12).  
==Current Research==


==Cell structure and metabolism==
Currently, ''R. metallidurans'' are being studied for their potential in fuel cell production (12). Also, as mentioned above, this microbe has the unique ability to precipitate gold. Current research is trying to better understand this interesting characteristic(1). Furthermore, ''R. metallidurans'' has been studied for its use in the prevention of lead contamination by the fluorescent signaling of its lead binding protein (11).
Recently, several authors have reported the use of PCR-ribotyping (3, 5, 7, 8, 12, 22, 23) and PCR-restriction fragment length polymorphism (PCR-RFLP) analysis (20, 21) for strain differentiation within various bacterial species. Thus, an evaluation for the ability of these two techniques to distinguish between R. paucula strains and between strains belonging to other Ralstonia species (R. eutropha, R. pickettii, R. gilardii, and R. solanacearum) is going on. As the ribosomal DNA (rDNA) intergenic spacer can contain genes coding for tRNA (15, 24), we also explored this region in R. paucula and compared it to those of other Ralstonia species.


''Ralstonia metallidurans'' uses a variety of substrates as its carbon source. It can grow chemo-lithotropically using molecular hydrogen as the energy source and carbon dioxide as a carbon source to form a cytoplasmic NAD-reducing and a membrane-bound hydrogenase. It contains most metabolic attributes; however, it does not grow on fructose (4). ''R. metallidurans'' can reduce selenite to elemental red selenium, metabolize  glutamatee, ascorbate, aldarate and nitrogen. When nitrate is present ''Ralsonia metallidurans'' can grow anaerobically. Its optimal growth temperature is 30 çC.
==References==


''Ralstonia metallidurans'' is rod-shaped, motile aerobe. It is a gram-negative bacteria which contains certain cell wall characteristics such as containing peptidoglycan. Cells are also surrounded by an outer membrane containing lipopolysaccharide (5). Porins exist in the outer membrane, which act like pores for particular molecules (5). There is a space between the layers of peptidoglycan and the secondary cell membrane called the periplasmic space (5). The S-layer is directly attached to the outer membrane, rather than the peptidoglycan and no teichoic acids or lipoteichoic acids are present.  
1.Llyod, Robin. "Eureka! Bacteria Have the Midas Touch" 18 July 2006.  
www.livescience.com/strangenews/060718_gold_bacteria


[[Image:Cationicpeptides(1).gif|thumb|300px|center|'' Cell structure of a gram-negative bacterium such Ralstonia metalidurans .''. [www.scq.ubc.ca/.../08/cationicpeptides(1).gif]]]
2.Larsen, Rachel and Kit Pogliano. "Outside structures 1: cell wall and membranes." BIMM 120: Introductory Microbiology. University of California, San Diego. Spring 2007.  


==Ecology==
3. M Mergeay. "Alcaligenes eutrophus CH34 is a facultative chemolithotroph with plasmid-bound resistance to heavy metals." J Bacteriol. April 1985
http://jb.asm.org/cgi/content/abstract/162/1/328


Due to its extremophilic ability to withstand high concentrations of heavy metals it renders it as a potential agent of bioremediation of soil and water contaminated with these toxic heavy metals or chlorinated organic compounds. It also points towards being an ideal model organism for understanding metal resistance phenotypes.
4. "Cupriavidas metallidurans CH34" JGI Microbes
http://genome.jgi-psf.org/draft_microbes/ralme/ralme.home.html


Lead contamination in our food and water is a serious threat to human health and the environment. Typically, lead levels are measured by using atomic absorption spectroscopy. The recenent finding of a fluorescent Lead II Probe from Lead II-regulatory protein isolated from ''Ralstonia metallidurans'' could provide rapid, on-site evaluation of the lead content of a sample.
5. http://genome.jgi-psf.org/finished_microbes/ralme/ralme.home.html


==Pathology==
6. genome.bnl.gov/sequencing/Rmetallidurans


''Ralstonia metallidurans'' is not a pathogen and does not inhabit any host organisms. However, many other species of Ralsontonia can be pathogenic, some to plants (''Ralstonia solanacearum'')<br /> and even others that have been seen in cystic fibrosis patients(''Ralstonia pickettii''). Many species of Gram-negative bacteria like ''R. metallidurans'' are pathogenic to other organisms. This pathogenic capability is usually associated with the structural components of gram-negative cell walls, in particular the lipopolysaccharide (also known as LPS or endotoxin) layer. The LPS is the trigger which the body's innate immune response receptors sense to begin a cytokine reaction which is toxic to the host.
7.skcen.be/sckcen_en/activities/research/radiationprotection/radiobio/ralmet


==Application to Biotechnology==
8. genome.jp/kegg-bin/show_organism?org=rme


Interestingly, enzymes from ''Ralstonia metallidurans'' were used by scientists in constructing a fuel cell (3).  "By encasing a pair of electrodes coated with these enzymes from ''Ralstonia metallidurans'' which oxidize hydrogen put inside a container filled with air and 3 percent more hydrogen" (3). Trials of the fuel cell produced enough electricity to make a watch function and larger scale productions are thought to be possible and are in the making.  
10. M Mergeav. "Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes." FEMS Microbial Rev. June 2003
http://ncbi.nlm.nih.gov/sites/entrez?


[[Image:060802103513.jpg|thumb|300px|right|''Colored scanning electron image of bacterioform gold on a gold grain from the Hit or Miss Mine in northern Queensland''. [http://images.livescience.com/images/060718_gold_bacteria_01.jpg]]]
11. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC87738/


==Current Research==
cmd=Retrieve&db=PubMed&list_uids=12829276


It is being researched that ''Ralstonia metallidurans'' could be involved in precipitating gold out of solution. It has the innate ability to thrive in gold concentrations that would kill most other organisms(1). "It is possible that the microbe screens out the gold as part of an effort to detoxify its immediate environment"(1).  
11. bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=05-33


==References==
12. American Chemical Society."New 'biofuel cell' produces electricity from hydrogen in plain air."26 March 2007. http://www.physorg.com/news94144517.html


1.Llyod, Robin. "Eureka! Bacteria Have the Midas Touch" 18 July 2006. http://www.livescience.com/othernews/060718_gold_bacteria.html
Edited by Shu-Mei (April) Yu student of[mailto:ralarsen@ucsd.edu Rachel Larsen] and Kit Pogliano.


2."Ralstonia metallidurans." March 2002. BrookHaven National Labratory. http://genome.bnl.gov/Sequencing/Rmetallidurans/


3.American Chemical Society."New 'biofuel cell' produces electricity from hydrogen in plain air."26 March 2007. http://www.physorg.com/news94144517.html
KMG
4. M Mergeay. "Alcaligenes eutrophus CH34 is a facultative chemolithotroph with plasmid-bound resistance to heavy metals."  J Bacteriol. April 1985
http://jb.asm.org/cgi/content/abstract/162/1/328


5. Larsen, Rachel and Kit Pogliano. "Outside structures 1: cell wall and membranes." BIMM 120: Introductory Microbiology. University of California, San Diego. Spring 2007.
<!-- Do not edit or remove this line-->[[Category:Pages edited by students of Mary Glogowski at Loyola University]]
Edited by student of [mailto:ralarsen@ucsd.edu Rachel Larsen] and Kit Pogliano

Latest revision as of 15:21, 7 July 2011

This is a curated page. Report corrections to Microbewiki.

A Microbial Biorealm page on the genus Ralstonia metallidurans


Classification

Higher order taxa

Kingdom: Bacteria

Phylum: Proteobacteria

Class: Beta Proteobacteria

Order:Burkholderiales

Family: Ralstoniaceae

Genus: Ralstonia

Species: R. metallidurans

Strain: CH3

Species

NCBI: Taxonomy


Ralstonia basilensis
Ralstonia campinensis
Ralstonia eutropha
Ralstonia gilardii
Ralstonia insidiosa
Ralstonia mannitolilytica
Ralstonia paucula
Ralstonia pickettii
Ralstonia respiraculi
Ralstonia solanacearum
Ralstonia syzygii
Ralstonia taiwanensis


Description and significance

Ralstonia metallidurans is a gram-negative microbe that does not form spores. It is unique in that it can fluorish in millimolar concentrations of heavy metals, such as gold, that are normally toxic to bacteria. According to discoverer Frank Reith, Ralstonia metallidurans "is able to survive in concentrations of gold that would kill most other micro-organisms" (1). Not only can these microbes withstand toxic concentrations of metals, they are found to be able to precipitate gold. Although it is unknown exactly how this process works, it is "possible that the microbe screens out gold as part of an effort to detoxify its immediate environment" (1).

Ralstonia metallidurans and other metal resistant microbes are often found in sediments with a high content of heavy metals from diverse geographical locations. The reference strain, CH34, was first discovered in 1976, from the sludge of a zinc decantation tank in Belgium that was polluted with high concentrations of several heavy metals. Frank Reith (and colleagues) at Australian National University further isolated and grew the bacteria in the lab.

The significance of this microbe lays in that its genome contains plasmids that confer resistance to heavy metals, such as Zinc, Mercury, Cadmium, Cobalt, etc. In 1992, Kostman et al. developed a PCR-ribotyping method for B. cepacia which could detect significant polymorphisms in the intergenic 16S-23S spacer of rRNA genes (7). In 1997, Shreve et al. used PCR-RFLP analysis for the 16S and 23S regions of the rRNA genes in an epidemiological study of B. cepacia infection (21). Segonds et al. used PCR-RFLP analysis of the 16S rRNA gene to differentiate Burkholderia species (20).

Genome structure

The genome of R. metallidurans CH34 has been extensively studied. It contains two large plasmids that encode for heavy metal resistance. pMOL28 (163 kb) furnishes tolerance to Nickel, Mercury, and Cobalt; pMOL30 (238 kb) confers resistance to Zinc, Cadmium, Mercury, and Cobalt (3). These plasmids are self-transmissible in homologous matings, but at low frequencies (3). The entire genome is approximately 6900 kb in size. In addition to the plasmids pMOL28 and pMOL30, it also contains two circular chromosomes (8). Furthermore, the genome encodes "8 P-type ATPase involved in metal efflux specialized in lead, cadmium, thallium and/or copper efflux, and several other mechanism involved in metal processing" (1). Together, these genetic elements contribute to the microbe's unique ability to survive in harsh environments. The amplicons of R. paucula isolates were digested with AciI and AlwI. All of the strains shared a single pattern with each of the two endonucleases. The AciI pattern was composed of eight fragments (340, ~200, 122, 119, 92, 75, 49, and 44 bp), and the AlwI pattern was composed of four fragments (418, 218, 130, and 75 bp)

Cell structure and metabolism

R. metallidurans is a gram-negative bacillus (rod shaped). Therefore, it has the structural features of gram-negative bacteria, such as cell walls containing peptidoglycan, an outer membrane containing LPS and porins, and a periplasmic space (2).

R. metallidurans is able to utilize a variety of substrates as its carbon source. It can grow autotrophically using molecular hydrogen as an energy source and carbon dioxide as its carbon source. Furthermore, in the presence of nitrate, it can grow anaerobically (6). When grown lithoautotrophically on molecular hydrogen, it forms cytoplasmic NAD-reducing and membrane bound hydrogenase. It does not grow on fructose (3) and its optimal growth temperature is 30 C (4).

Ecology

Due to its ability to withstand toxic metals, R. metallidurans has been studied to utilize this characteristic in areas of bioremediation (10). Furthermore, new findings of a lead binding protein isolated from R. metallidurans is key in preventing lead poisoning (11).

Pathology

R. metallidurans has not been found to be pathogenic to humans. However, a near relative, R. solancearum, that shares some of the metal resistant genes, has been found to cause disease in plants (10). R. paucula has been isolated from pool water, groundwater, and bottled mineral water (2, 9, 17) and from clinical specimens. Despite its low pathogenicity, it is now recognized as an opportunistic pathogen which can generate serious infections such as septicemia, peritonitis, abscess, and tenosynovitis, particularly in immunocompromised patients

Application to Biotechnology

R. metallidurans has been found to produce enzymes that may be used in constructing a fuel cell (12). These enzymes are able to oxidize hydrogen, which can ultimately result in the production of electricity. Scientists are in the process of researching this phenomenom (12).

Current Research

Currently, R. metallidurans are being studied for their potential in fuel cell production (12). Also, as mentioned above, this microbe has the unique ability to precipitate gold. Current research is trying to better understand this interesting characteristic(1). Furthermore, R. metallidurans has been studied for its use in the prevention of lead contamination by the fluorescent signaling of its lead binding protein (11). Recently, several authors have reported the use of PCR-ribotyping (3, 5, 7, 8, 12, 22, 23) and PCR-restriction fragment length polymorphism (PCR-RFLP) analysis (20, 21) for strain differentiation within various bacterial species. Thus, an evaluation for the ability of these two techniques to distinguish between R. paucula strains and between strains belonging to other Ralstonia species (R. eutropha, R. pickettii, R. gilardii, and R. solanacearum) is going on. As the ribosomal DNA (rDNA) intergenic spacer can contain genes coding for tRNA (15, 24), we also explored this region in R. paucula and compared it to those of other Ralstonia species.

References

1.Llyod, Robin. "Eureka! Bacteria Have the Midas Touch" 18 July 2006. www.livescience.com/strangenews/060718_gold_bacteria

2.Larsen, Rachel and Kit Pogliano. "Outside structures 1: cell wall and membranes." BIMM 120: Introductory Microbiology. University of California, San Diego. Spring 2007.

3. M Mergeay. "Alcaligenes eutrophus CH34 is a facultative chemolithotroph with plasmid-bound resistance to heavy metals." J Bacteriol. April 1985 http://jb.asm.org/cgi/content/abstract/162/1/328

4. "Cupriavidas metallidurans CH34" JGI Microbes http://genome.jgi-psf.org/draft_microbes/ralme/ralme.home.html

5. http://genome.jgi-psf.org/finished_microbes/ralme/ralme.home.html

6. genome.bnl.gov/sequencing/Rmetallidurans

7.skcen.be/sckcen_en/activities/research/radiationprotection/radiobio/ralmet

8. genome.jp/kegg-bin/show_organism?org=rme

10. M Mergeav. "Ralstonia metallidurans, a bacterium specifically adapted to toxic metals: towards a catalogue of metal-responsive genes." FEMS Microbial Rev. June 2003 http://ncbi.nlm.nih.gov/sites/entrez?

11. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC87738/

cmd=Retrieve&db=PubMed&list_uids=12829276

11. bnl.gov/bnlweb/pubaf/pr/PR_display.asp?prID=05-33

12. American Chemical Society."New 'biofuel cell' produces electricity from hydrogen in plain air."26 March 2007. http://www.physorg.com/news94144517.html

Edited by Shu-Mei (April) Yu student ofRachel Larsen and Kit Pogliano.


KMG

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