| Summary: |
The sediments of the Housatonic River (Lenox, Massachusetts, USA) are contaminated with Aroclor 1260, a commercial polychlorinated biphenyl (PCB) mixture composed of mainly hexa- and heptachlorobiphenyls. We previously identified specific halogenated biphenyls that selectively stimulate indigenous microorganisms in these sediments to dechlorinate the PCBs by three different dechlorination processes (Processes N, P, and LP), which differ in congener selectivity, position of the chlorine removed, and terminal products. Here we summarize, further characterize, and compare dechlorination processes N, P, and LP. We also develop strategies to selectively enrich the microbial consortia responsible for each distinct dechlorination activity and eliminate many non-essential microorganisms. Pasteurization completely inhibited -Dechlorination processesN, Pand LP, but molybdate, which inhibits sulfate reducers, had little or no effect. Penicillin G and vancomycin did not inhibit dechlorination processes N or P, but streptomycin completely inhibited both. These and other data indicate that the PCB-dechlorinating bacteria responsible for dechlorination processes N, P, and LP are not spore-formers, and not sulfate reducers. We conclude that penicillin G, vancomycin, and molybdate can be used to selectively eliminate non-essential microorganisms, while the PCB-dechlorinating population is simultaneously enriched by repeated transfer using selective primers, temperature, and pH. Our findings lay the basis for developing highly enriched microcosms for each PCB dechlorination process. This research may lead to effective and environmentally compatible ways to accelerate the detoxification and degradation of PCBs in situ. |