| STUDY |
A bacterium that depends on reducing 1,1,1-trichloroethane (TCA) for sustenance is the latest addition to a line of microbes that can degrade chlorinated solvents. Identifying these bacteria and understanding their molecular biology is rapidly expanding the options for in situ remediation of soil and groundwater at Superfund and other waste sites. CHLORINE DIET Tiedje (left) and Sun pose with a culture vial of TCA1 in action against trichloroethane. MICHIGAN STATE PHOTO The bacterium, a Dehalobacter strain named TCA1, was isolated from river sediments. Dehalobacter bacteria, first described in 1994, couple their growth to the reduction of a chlorinated solvent using H2 as a reducing agent--a process called dehalorespiration. This process has been observed to degrade chloroethenes, chlorobenzenes, and 2-chlorophenol. But until now, dehalorespiration hasn't been reported for TCA. "TCA was one of the remaining groundwater pollutants for which biodegradation had not been resolved," Tiedje says. TCA1 can't survive without TCA present, he adds, and it's not active against chloroethenes. In anaerobic lab cultures, TCA1 reduced TCA to 1,1-dichoroethane and then to chloroethane over several weeks. In lab tests on soils taken from a contaminated site, TCA1 converted TCA to chloroethane in two months. Chloroethane can be degraded to CO2 and chloride ions by aerobic soil bacteria, the Michigan State researchers note, so a combination treatment could be carried out to clean up a contaminated site |
| UPDATE | 11.02 |
| AUTHOR |
Michigan State Uni.'s Center for Microbial Ecology - Sun Baolin - Tiedje James M. |
| LITERATURE REF. | [Science, 298, 1023 (2002)]. |
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