Mighty Microbe Attacks Water Pollution

An industrial chemical that pollutes groundwater and has resisted cleanup can be neutralized by an obscure microbe that researchers have discovered in the Hudson River bottom mud.

In a study appearing Friday in the journal Science, researchers at Michigan State University report a previously unknown bacteria is able to turn trichloroethane, an industrial chemical that is difficult to clear from ground water, into a more benign compound that other microbes can render harmless.

Benjamin M. Griffin, a Michigan State researcher and a co-author of the study, said the microbe reduces trichloroethane through respiration to chloroethane, a compound that is more easily cleared from groundwater.

"This microbe thrives in the presence of TCA (trichloroethane)," Griffin said. In laboratory experiments, he said, the microbe is grown by adding TCA to its culture medium.

The microbe lives in the absence of oxygen, which means it could would be useful for cleaning TCA from aquifers and groundwater where the chemical is a common pollutant, said Griffin. TCA is present in 696 of 1430 cleanup priority sites identified by the Environmental Protection Agency. The chemical is used as an industrial solvent.

"TCA was one of the remaining groundwater pollutants for which biodegradation has not been resolved," James Tiedje, the senior author of the study, said in a statement. "Till now, there wasn't good evidence there was a biodegradable solution."

John Doull, a toxicologist at the University of Kansas who was not involved in the research said that "any mechanism that can clean up residues and solvents is helpful and significant. He noted, however, that TCA is not considered as environmentally troublesome as tetrachloroethene or trichloroethene, two other industrial chemicals often found in groundwater.

In a laboratory experiment, the Michigan State researchers tested the response of the microbe in groundwater sediments that were contaminated with TCA. Over a two-month period, the busy microbe completely converted all the TCA in the sediments to another, less hazardous compound, said Griffin.

By Paul Recer