GENETICALLY modified bacteria capable of cleaning up soil contaminated with toxic solvent residues have come a step closer with the publication of the genome sequence of a sewage-dwelling bug.

The bacterium Dehalococcoides ethenogenes is already being used inpilot projects on contaminated sites to remove perchloroethene (PCE) and trichloroethene (TCE) from the soil. These solvents were once thought to be inert and harmless, and were dumped in large quantities in the 1950s and 1960s. "Then it emerged that they were both neurotoxic and carcinogenic," says Stephen Zinder of Cornell University in Ithaca, New York. "Every dry-cleaning store in the US probably has a PCE spill associated with it," he says. TCE contaminates airfields, where it was used to degrease aircraft parts.

Sites undergoing treatment with D. ethenogenes include the Kelly Air Force base in San Antonio, Texas, and a derelict industrial site in Caldwell, New Jersey. Although the bug appears to ...