Stimulation and enrichment of two microbial polychlorinated biphenyl reductive dechlorination activities

Isolation and characterization of the bacterium or bacterial consortium responsible for microbial polychlorinated biphenyl (PCB) reductive dechlorination would allow a better understanding of the mechanism of this activity in the environment. Stimulation and enrichment of a PCB dechlorination activity in a culture is necessary for isolation of the microorganisms that cause PCB dechlorination. Two distinct microbial PCB dechlorination activities were independently stimulated in slurries of PCB-contaminated upper Hudson River sediment by adding specific PCB congeners. The addition of 2,4,6-trichlorobiphenyl stimulated a specific para dechlorination activity on Aroclor 1242 (designated a Process Q). In contrast, 2,3,6-trichlorobiphenyl addition stimulated a specific meta dechlorination activity (designated a Process M). Each dechlorination activity was enriched by transferring 10 percent by volume of the sediment slurry containing the dechlorination activity to an autoclaved medium composed of an anaerobic mineral solution, humic acids, and PCBs. This is the first report of an enrichment culture of the microbial para dechlorination activity (the Process Q). Both microbial PCB dechlorination activities were inhibited by vancomycin (5 ppm) or nisin (500 ppm). These data suggest that a population of gram-positive bacteria is essential for these PCB dechlorination activities.