The history of anaerobic microbial polychlorinated biphenyl (PCB) dechlorination is traced over 20 years using a case study of PCB dechlorination in the Housatonic River (Massachusetts) as an example. The history progresses from the characterization of the PCBs in the sediment, to cultivation in sediment microcosms, to the identification of four distinct types of PCB dechlorination, to a successful field test, to the cultivation in defined medium of the organisms responsible for extensive dechlorination of Aroclor 1260, and finally to the identification of a Dehalococcoides population that links its growth to the dechlorination of Aroclor 1260. Other PCB dechlorinators have also been identified. Two bacterial strains, o-17 and DF-1, that link their growth to the dechlorination of several PCB congeners belong to a novel clade of putative dechlorinating bacteria within the phylum Chloroflexi. Dehalococcoides ethenogenes strain 195 also dechlorinates several PCB congeners when grown on chlorinated ethenes. Evidence is mounting that Dehalococcoides and other dechlorinating Chloroflexi may play a significant role in the dechlorination of commercial PCBs in situ.
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Article Synopsis
- * The addition of ADS significantly boosted the rate of dechlorination for Aroclor 1260, particularly increasing the removal of meta- and para-chlorine while not altering the dechlorination pathways.
- * The research also found that ADS led to an increased abundance of important dechlorinating bacteria and associated functional genes, suggesting its potential in isolating and enriching organohalide-respiring bacteria (OHRB) through supplemental techniques.
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