The study of the DNA sequence of Dehalococcoides ethenogenes, which appears in the January 7 issue of Science, found evidence that the soil bacterium may have developed the metabolic capability to consume chlorinated solvents fairly recently possibly by acquiring genes in an adaptation related to the increasing prevalence of the pollutants.
"The genome sequence contributes greatly to the understanding of what makes this microbe tick and why it's metabolic diet is so unusual," says TIGR scientist Rekha Seshadri, the primary author of the Science paper.
D. ethenogenes, which was discovered by Cornell University scientists at a sewage treatment plant in Ithaca, NY, is the only known microbe that is known to reductively dechlorinate the pervasive groundwater pollutants tetrachloroethelene (PCE) and trichloroethylene (TCE). That dechlorination produces a nontoxic byproduct, ethene.
A collaborator on the sequencing project is Cornell microbiologist Stephen Zinder, whose lab was the first to isolate the bacterium. Another major collaborator was Lorenz Adrian of the Institute for Biotechnology at the Technical University of Berlin, Germany. The D. ethenogenes project was sponsored by the U.S. Department of Energy's Office of Biological Energy Research.
Studies by Zinder and others have shown that members of the genus Dehalococcoides are necessary for complete dechlorination of PCE and TCE at contaminated sites.
"When I first looked at a purified PCE-degrading culture under a microscope, the tiny organism looked like junk to me," says Zinder. "I never dreamed I'd some day we'd know the genome sequence of that 'junk.' "
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