Ralstonia metallidurans

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

[Others may be used.  Use NCBI link to find]

Species

NCBI: Taxonomy

Genus species Ralstonia metallidurans

Description and significance

Ralstonia metallidurans is a gram-negative, non-spore forming bacillus that flourishes in millimolar concentrations of toxic 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. The reference strain, 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. Ralstonia metallidurans was identified by Frank Reith of Australian National University and his colleagues as the common denominator among bacteria comprising a dried organic biofilm found on the surface of gold grains collected from a park and gold mines in southern New South Wales and northern Queensland, Australia. Reith further isolated and grew the bacteria in the lab and found that R. metallidurans have the unique ability to precipitate gold. According to Reith, "A unique attribute of R. metallidurans is that it is able to survive in concentrations of gold that would kill most other micro-organisms." Metals like gold are normally toxic to bacteria. It is still unknown exactly how the bacteria help to precipitate the gold grains, but is possible that the microbe screens out the gold as part of an effort to detoxify its immediate environment. Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.

Genome structure

A typical feature of these metal-resistant Ralstonia is the presence of one or two large megaplasmids which contain genes for multiple resistances to heavy metals. The reference strain, CH34, contains two large plasmids, pMOL28 (180 kb) and pMOL30 (240 kb). Together these plasmids confer resistance to Zn, Cd, Co, Pb, Cu, Hg , Ni and Cr. Both plasmids are low copy number and stably maintained even without selective pressure. They are self-transferable at low frequencies.

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Cell structure and metabolism

Its optimal growth temperature is 30 çC. As discussed above, an interesting characteristic of R. metallidurans is their ability to thrive in millimolar concentrations of heavy metals which are normally toxic to microbes. Furthermore, this bacteria contributes to the formation of gold.

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Ecology

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Pathology

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Application to Biotechnology

Does this organism produce any useful compounds or enzymes? What are they and how are they used?

Current Research

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References

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500. http://en.wikipedia.org/wiki/Cupriavidus_necator http://genome.jgi-psf.org/draft_microbes/ralme/ralme.home.html http://www.livescience.com/othernews/060718_gold_bacteria.html Edited by Shu-Mei (April) Yu, student of Rachel Larsen and Kit Pogliano