Understanding the genetic makeup of microbes that thrive in polluted environments may one day help scientists engineer bacteria that can clean contaminants from soil. In a step toward that goal, the U.S. Department of Energys Joint Genome Institute (JGI) has just released the draft gene sequence of one such toxin-tolerant bug. The bacterium, known as Ralstonia metallidurans, is being deciphered by John Dunn and Geoffrey Hind, biologists at DOEs Brookhaven National Laboratory, in collaboration with scientists in Belgium and others at JGI.
This bacterial strain was first isolated in 1976, from the sludge of a settling tank in Belgium that was polluted with high concentrations of heavy metals. Examination revealed that, in addition to its chromosomal genes, Ralstonia has two large plasmids genetic material that is separate from the chromosomal genes necessary for ordinary cell function. According to Dunn, these plasmids house genes that make Ralstonia resistant to the harmful effects of a wide array of heavy metals, including zinc, cadmium, cobalt, lead, copper, mercury, nickel, and chromium.
Having a draft sequence of the Ralstonia genome, which contains some 3,000 genes, will make manipulation of these naturally existing resistance factors much more practicable, says Dunn. Eventually, well want to understand how these genes are regulated under a variety of growth conditions and in different environments to see how they might be applied in bioremediation.
For example, through genetic engineering, scientists might be able to transfer the heavy-metal-resistant genes from Ralstonia into other microbes that decompose organic pollutants. Or alternatively, the scientists might use Ralstonia as a host for other bacterial genes that would enable it to break down a variety of pollutants. In either case, the result would be bacterial strains with a combination of traits, ones that can tolerate heavy metals in a polluted environment while digesting org
Contact: Karen McNulty Walsh
DOE/Brookhaven National Laboratory