Identification of PCB enhanced microbial consortium from estuarine and freshwater sediments that undergo selective reductive dechlorination through Aroclor™ stimulation

Polychlorinated biphenyls (PCBs) are anthropogenic chemicals found in marine and freshwater sediments that have been contaminated through many decades. PCB exposure to human and animal populations is especially of concern due to the ability of this toxic waste to persist and bioaccumulate. In previous studies we have shown that commercial mixtures of PCBs, known as Aroclors, are dechlorinated to less chlorinated congeners by a microbial respiratory process called reductive dechlorination. However, the effect of different Arclor mixtures on the composition of the bacterial community is not well understood. The purpose of my project is to characterize the PCB dechlorinating bacteria community enriched by different Aroclor mixtures. Microcosms of Baltimore Harbor, Grasse River, and Fox River sediments were created under anaerobic conditions and challenged with Aroclor 1260, 1248, and 1242 congener mixtures. The reductive dechlorination products will be monitored by electron capture gas chromatography to identify the dehalogenating pathways. The composition of the microbial community selectively enriched by each Aroclor within the active dechlorinating microcosms will be characterized with denaturing gradient HPLC. Further analysis via quantitative PCR will quantify the PCB dechlorinating microbial phylotypes. The preliminary results of this study are presented.