The document summarizes research on the dechlorination of polychlorinated biphenyl (PCB) congeners by the anaerobic bacterium Dehalococcoides. Key findings include: 1) Dehalococcoides uses PCBs as a terminal electron acceptor and can effectively dechlorinate various PCB mixtures. 2) Experiments showed some PCB congeners (234 CB and 2345 CB) underwent more dechlorination than others (245 CB and 235 CB). 3) Further research is needed to understand congener specificity and identify reductive dehalogenase enzymes responsible for dechlorinating different PCBs.