Novel Bacterium Detoxifies Harmful Chlorinated Compounds

The finding opens the door for designing more efficient and successful bioremediation strategies for thousands of contaminated sites that remain threats, despite years of expensive cleanup work.

"This organism might be useful for cleaning contaminated subsurface environments and restoring drinking-water reservoirs," Georgia Institute of Technology researchers report in the July 3, 2003 issue of the journal Nature.

The paper, titled "Detoxification of vinyl chloride to ethene coupled to growth of an anaerobic bacterium" is the culmination of five years of field and laboratory studies funded by the National Science Foundation and the Strategic Environmental Research and Development Program.

Scientists and engineers have struggled for years with clean up of groundwater and subsurface environments contaminated decades ago by unregulated use of the common solvents tetrachloroethene (PCE) and trichloroethene (TCE). These toxic compounds are primarily used in dry cleaning operations and degreasing of metal components. Complicating the situation are natural biotic and abiotic processes that transform these solvents to intermediate substances, such as toxic dichloroethenes, and cancer-causing agents, such as vinyl chloride.

But in a step toward engineering better bioremediation strategies, Georgia Tech researchers have isolated a naturally occurring bacterium, designated Dehalococcoides strain BAV1, in a pure culture - without other microbial species present in the sample. Though some progress was made in the past decade in understanding the bacteria involved in partial degradation of PCE and TCE, this study represents a significant advance, researchers said.

"Isolating this bacterium will allow us to study the organism and the dechlorination process in more detail," said lead researcher Frank Loeffler, an assistant professor in the School of Civil and Environmental Engineering. "We can get a lot more information that we can then use to engineer systems in the environment so PCE and TCE degradation would not stop at the toxic intermediate stage, but rather would continue to be dechlorinated to a non-toxic end product, such as ethene."

One site that appears likely to benefit from in-place bioremediation with this bacterium is the Bachman Road residential area contaminated with PCE by a former dry cleaning operation in Oscoda, Mich. There, researchers recently used BAV1 in a successful pilot demonstration, which they briefly reference in the Nature paper. Loeffler and his colleagues described the results of the pilot study in greater detail in a paper published in February 2003 in the journal Environmental Science & Technology.

At this contaminated site, PCE penetrated the water table and contaminated drinking-water wells in the area. The contaminants also migrated through the groundwater into nearby Lake Huron.