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