For just about every substance, there's a microbe that eats it. That's even true for man-made pollutants that didn't exist 60 years ago.
Take Dehalococcoides ethenogenes. In 1997, microbiologist Steve Zinder of Cornell University isolated the microbe from sewage sludge contaminated with the chemical tetrachloroethene (PCE). The strain, it turned out, consumes PCE or its chemical cousin, the engine-degreasing chemical trichloroethene (TCE), as food. The chemicals are widely used by dry cleaners, electronics companies, and the military.
Since neither chemical existed in nature prior to World War II, Zinder, microbiologists Rekha Seshadri and John Heidelberg of The Institute of Genomic Research in Rockville, Maryland, and their colleagues wondered how the bug could have evolved such talents. They also realized that sequencing the microbe's genome could yield insights into the microbe's metabolism. Such clues would likely help scientists refine strains to clean up the many aquifers polluted by PCE and TCE, which can cause neurological damage and cancer.
Their work, published in the 7 January issue of Science , found 17 genes that help break down PCE, TCE, and related compounds by plucking off chlorine atoms, but none of the genes that help other microbes feast happily on more common food like sugar and oxygen. What's more, almost all of the detoxifying genes were associated with other genes that form an elaborate on-off switch that may help the bug sense chlorinated compounds.
The results show how the microbe is highly specialized to live on PCE, TCE, and their chemical cousins. And four of the 17 dechlorination genes sit in a long stretch of the genome that contains genetic elements known informally as jumping genes, which can carry nearby genes from one microbe to another. That means that the microbe evolved its unusual talents "fairly recently," Seshadri says.
"I think it's excellent" work, says microbial ecologist Jim Tiedje of Michigan State University. PCE and TCE are hard to remove because they sink to the bottom of aquifers. Dehalococcoides, he says, offers "probably the only chance we have to clean up some of our aquifers."
Background on bioremediation from the United States Geological Survey 
More background on bioremediation from Cornell University, with links 
"A Citizen's Guide to Bioremediation" from the U.S. EPA. [pdf file]