Bacteria breathe chlorine pollutants from groundwater

Scientists have discovered bacteria that thrive on the pollutant trichloroethane (TCA) and could be used to clean up TCA-contaminated land and water. A microcosm study has shown that adding the bacteria to an aquifer degrades TCA that is otherwise persistent.

US scientists at Michigan State University showed that the bacterium uses TCA and hydrogen to produce energy in the absence of oxygen, effectively ‘breathing’ the TCA through a process known as dehalorespiration. Their discovery, published in the latest issue of Science, suggests the organism would be ideal for cleaning up contaminated soil and groundwater.

Research groups have studied the biological degradation of TCA for a number of years, Dr James Tiedje of Michigan University told edie. “But the importance of our finding is that we have a pure strain of a bacterium that grows on the energy released during the degradation of TCA.” In other words, the bacterium thrives on the breakdown of TCA, multiplying itself as TCA is consumed.

Dr Tiedje says the discovery offers yet more promise for bioremediation as a useful clean-up tool. “Companies already performing in-situ bioremediation projects for other pollutants could readily incorporate this bacterium into bioaugmentation clean-up strategies,” he argues.

Microbial-based strategies are often favourable because of their effectiveness and relatively low cost, says Tiedje, although for severely contaminated sites, biological activity is usually inhibited. Nevertheless, in the best-case scenario the bacterium could be used to clean-up polluted groundwater or wastewater in a matter of months, he says.

The new bacterium is closely related to those that consume industrial solvents similar to TCA. Dr Tiedje says that there is no evidence suggesting that chlorinated solvent degrading bacteria have adverse effects on soil or groundwater.

According to the authors, nearly half of US Environmental Protection Agency Superfund sites are contaminated with TCA, a suspected carcinogen that also contributes to ozone destruction. “Several hundred sites in the US alone are polluted with TCA,” says Tiedje.

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