Bacteria can cut PCB contamination
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The microbes replace the chlorine atoms with hydrogen It might take a few years to degrade PCBs using the microbes
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AROCLOR 1260 is a common, highly chlorinated PCB (polychlorinated biphenyl) mixture. Researchers have identified a group of bacteria that can detoxify this common type of PCB, which has contaminated more than 250 U.S. sites, including river and lake sediments.
Researchers have known for more than two decades that naturally occurring microorganisms could slowly dechlorinate PCBs, which were once commonly used by industry.
The research results will be published April 15 in the journal Applied and Environmental Microbiology. In research funded by the National Science Foundation and General Electric, a PCB expert at Rensselaer Polytechnic Institute (RPI) collaborated with microbiologists at the Georgia Institute of Technology.
They studied microbial degradation in Aroclor 1260. RPI Professor of Biology Donna Bedard collected PCB-contaminated sediment samples.
Microcosm studies
In microcosm studies in her lab, Bedard found that Aroclor 1260 was indeed being degraded by native sediment microbes, and she developed sediment-free enrichment cultures.
She then worked with Georgia Tech researchers Frank Loeffler and Kirsti Ritalahti to further characterize these Aroclor 1260-dechlorinating enrichment cultures.
Through a series of experiments, the team was able to determine that bacteria in the Dehalococcoides (Dhc) group were responsible for the dechlorination of Aroclor 1260.
Replace chlorine atoms
These microbes replace the chlorine atoms in Aroclor 1260 with hydrogen, which fuels their growth and initiates the PCB degradation process, explained Loeffler, an associate professor in the School of Civil and Environmental Engineering and the School of Biology.
The research indicates that the Dhc bacteria active in the enrichment cultures also contribute to PCB dechlorination in situ (that is, in the Housatonic River sediment), according to a Georgia Tech press release.
Once Dhc bacteria dechlorinate Aroclor 1260 to a certain level, other microbial species will degrade it further and completely detoxify PCBs, Loeffler added.
Loeffler is optimistic about a bioremediation strategy for PCBs because of his lab's earlier success in identifying microbes that degrade the common solvents tetrachloroethene (PCE) and trichloroethene (TCE).
More complicated
"The situation with PCBs is a little more complicated because they are in river and lake sediments instead of groundwater and subsurface environments, but in principle, the same sequence of events could occur," Loeffler said.
"We need industry, engineers and scientists to work together to develop a bioremediation approach for PCBs." — Our Bureau
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