Bacteria give up genetic secrets

The bug first found in sewage sludge may have evolved its talents in response to contamination of environment, say researchers.

A pollution-eating bacterium first found in sewage sludge may have evolved its talents in response to human contamination of the environment, researchers said on Thursday.

They published the genetic sequence of the bug, called Dehalococcoides ethenogenes Strain 195, and said it showed some surprising flexibility.

'The genome sequence contributes greatly to the understanding of what makes this microbe tick and why its metabolic diet is so unusual,' said Rekha Seshadri of The Institute for Genomic Research in Maryland, who helped lead the study.

D ethenogenes, discovered by a team at Cornell University in New York, is being used at 17 polluted sites in 10 states.

Different strains break down perchloroethylene or PCE, a chlorinated solvent used for dry cleaning; trichloroethylene, used to clean metal parts; chlorobenzenes, used to produce the now-banned pesticide DDT; and polychlorinated biphenyls or PCBs, compounds that were once used as coolants and lubricants in transformers.

'Because chlorinated solvents have polluted so many water sources, there is a pressing need for new techniques to clean up such pollutants,' said John Heidelberg of The Institute for Genomic Research, who has helped decode the genomes of other pollution-eating bacteria including the radiation-loving Deinococcus radiodurans.

The researchers, including teams at Cornell, Johns Hopkins University and Technical University in Berlin, found genes for 19 different reductive dehalogenases, enzymes that help D ethenogenes microbe 'breathe' chlorinated solvents.

It has clusters of genes called mobile genetic elements, said Cornell professor of microbiology Stephen Zinder, who named the bacteria after it was found in a sewage treatment plant.

'Just by picking up these mobile genetic elements from other bacteria, Dehalococcoides strains seem able to adapt and to take advantage of opportunities as they present themselves,' Zinder said in a statement.

The researchers said their findings suggest the bacteria may have developed the ability to munch chlorinated solvents fairly recently, the researchers said.