2 ANAEROBIC POLYCHLORINATED BIPHENYL-DEHALOGENATING ENRICHMENTS THAT EXHIBIT DIFFERENT PARA-DECHLORINATION SPECIFICITIES

Two anaerobic polychlorinated biphenyl (PCB)-dechlorinating enrichment s with distinct substrate specificities were obtained: a 2,3,4,6-tetra chlorobiphenyl (2346-CB) para-dechlorinating enrichment derived from A roclor 1260-contaminated Woods Pond (Lenox, Mass.) sediment and a 2,4, 6-trichlorobiphenyl (246-CB) unflanked para-dechlorinating enrichment derived from PCB-free Sandy Creek Nature Center (Athens, Ga.) sediment . The enrichments have been successfully transferred to autoclaved soi l slurries over 20 times by using 300 to 350 mu M 2346-CB or 246-CB. B oth enrichments required soil for successful transfer of dechlorinatio n activity. The 2346-CB enrichment para dehalogenated, in the absence or presence of 2346-CB, only 4 of 25 tested para halogen-containing co ngeners: 234-CB, 2345-CB, 2346-CB, and 2,4,6-tribromobiphenyl (246-BrB ). In the presence of 246-CB, the 246-CB enrichment para dehalogenated 23 of the 25 tested congeners. However, only three congeners (34-CB, 2346-CB, and 246-BrB) were dehalogenated in the absence of 246-CB, ind icating that these specific congeners initiate dehalogenation in this enrichment culture. The addition of the 2346-CB (para)-dechlorinating enrichment did not further stimulate the 2346-CB-primed dechlorination of the Aroclor 1260 residue in Woods Pond sediment samples. Compared to the addition of the primer 246-CB or the 246-CB unflanked para-dech lorinating enrichment alone, the addition of both 246-CB (300 mu M) an d the 246-CB enrichment stimulated the unflanked para dechlorination o f the Aroclor 1260 residue in Woods Pond sediments. These results indi cate that the two enrichments contain different PCB-dechlorinating org anisms, each with high substrate specificities. Furthermore, bioaugmen tation with the enrichment alone did not stimulate the desired dechlor ination in PCB-contaminated Woods Pond sediment.