Ralstonia metallidurans: Difference between revisions

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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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Kingdom: Bacteria
Kingdom: Bacteria
Phylum: Proteobacteria
Phylum: Proteobacteria
Class: Beta Proteobacteria
Class: Beta Proteobacteria
Order:Burkholderiales
Order:Burkholderiales
Family: Ralstoniaceae
Family: Ralstoniaceae
Genus: Ralstonia
Genus: Ralstonia
Species: R. metallidurans
Species: R. metallidurans
Strain: CH3
Strain: CH3


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Ralstonia solanacearum
Ralstonia oxalatica
Ralstonia paucula
Ralstonia pickettii


''Genus species''
''Ralstonia basilensis ''<br/ >
''Ralstonia campinensis''<br/ >
''Ralstonia eutropha''<br/ >
''Ralstonia gilardii''<br/ >
''Ralstonia insidiosa''<br/ >
''Ralstonia mannitolilytica''<br/ >
''Ralstonia paucula''<br/ >
''Ralstonia pickettii''<br/ >
''Ralstonia respiraculi''<br/ >
''Ralstonia solanacearum''<br/ >
''Ralstonia syzygii''<br/ >
''Ralstonia taiwanensis''<br/ >
 


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


The reference strain of Ralstonia Metallidurans, CH34, 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 geographical locations.
''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).
 
Alcaligenes eutrophus CH34, was just recently renamed Ralstonia. Ralstonia metallidurans is gram-negative, non-spore forming bacterium which thrives in the presence of millimolar concentrations of several heavy-metals; Zn, Cd, Co,Pb,Hg, Ni and Cr.  
 
This extremophile is better able to withstand high concentrations of heavy metals than any other well-studied organism. This fact renders it a potential agent of bioremediation as well as an ideal model organism for understanding metal resistance phenotypes. Due to its survival in extreme metal concentrations and genomic sequencing  it is thought to be one of the first life forms on earth.


''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==
==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)


The heavy-metal resistance found in these bacteia is conferred by two large megaplasmids (pMOL28=180 kbp and pMOL30=240 kbp) carrying gene clusters that encode cation-efflux machinery spanning both bacterial membranes. These low-copy number plasmids are maintained in the presence or absence of selective pressure and are self-transferable at relatively low frequencies. The Minimal Inhibitory Concentration (MIC) for free, non-chelated Ni, Co, Zn and Cd are 2.5, 20, 12 and 2.5 mM, respectively for the reference strain.
==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).


The genome of this bacterium contains also 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.  
''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).


Scientisist  have analysed the genome of Ralstonia metallidurans for genes encoding homologues of established and putative transport proteins; 13% of all genes in Ralstonia metallidurans encode such homologues. Nearly one-third of the transporters identified (32%) appear to function in inorganic ion transport with three-quarters of these acting on cations. Transporters specific for amino acids outnumber sugar transporters nearly 3 : 1, and this fact plus the large number of uptake systems for organic acids indicates the heterotrophic preferences of these bacteria. Putative drug efflux pumps comprise 10% of the encoded transporters, but numerous efflux pumps for heavy metals, metabolites and macromolecules were also identified.
==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).


==Cell structure and metabolism==
==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


Ralstonia metallidurans uses a variety of substrates as its carbon source or it can grow chemo-lithotropically using molecular hydrogen as the energy source and carbon dioxide as a carbon source. When nitrate is present Ralsonia metallidurans can grow anaerobically.  
==Application to Biotechnology==
Its optimal growth temperature is 30 çC.
''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==


==Ecology==
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.


Due to its ability to withstand high concentrations of heavy metals it renders it as a potential agent of bioremediation of soil and water contaminated with heavy metals or chlorinated organic compounds as well as an ideal model organism for understanding metal resistance phenotypes.
==References==


Lead contamination is a serious threat to human health and the environment. Lead levels are typically measured by using atomic absorption spectroscopy or other related instrumental methods. Developent of 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.
1.Llyod, Robin. "Eureka! Bacteria Have the Midas Touch" 18 July 2006.  
www.livescience.com/strangenews/060718_gold_bacteria


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


Ralstonia metallidurans is not a pathogen and does not inhabit any host organisms.
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


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


Interestingly, enzymes from Ralstonia metallidurans were used by scientists in constructing a fuel cell. 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. Trials of the fuel cell produced enough electricity to make a watch work. Larger scale productions are thought to be possible and are in the making.  
5. http://genome.jgi-psf.org/finished_microbes/ralme/ralme.home.html


It is also thought that Ralstonia metallidurans is thought to precipitate gold out of solution. It has an ability to survive in gold concentrations that would kill most other organisms.  
6. genome.bnl.gov/sequencing/Rmetallidurans


[[[[Image:060802103513.jpg|thumb|300px|left|''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]]]
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


==Current Research==
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 of[mailto:ralarsen@ucsd.edu Rachel Larsen] and Kit Pogliano.


==References==


http://www.livescience.com/othernews/060718_gold_bacteria.html
KMG
www.physorg.com/news94144517.html


Edited by student of [mailto:ralarsen@ucsd.edu Rachel Larsen] and Kit Pogliano
<!-- Do not edit or remove this line-->[[Category:Pages edited by students of Mary Glogowski at Loyola University]]

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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