CENSUS – Chlorinated Phenols Table
Detect and quantify bacteria responsible for biodegradation of Chlorinated Phenols
Pentachlorophenol (PCP) was one of the most widely used biocides in the US and despite residential use restrictions is still extensively used industrially as a wood preservative. Along with PCP, the tetrachlorophenol and trichlorophenol isomers were also used as fungicides in wood preserving formulations. 2,4-dichlorophenol and 2,4,5-TCP were used as chemical intermediates in herbicide production (e.g. 2,4-D) and chlorophenols are known byproducts of chlorine bleaching in the pulp and paper industry.
Under aerobic conditions, PCP can be utilized as a sole source of carbon and energy by some bacteria. PCP biodegradation is initiated by PCP 4-monooxygenase (PcpB) followed by two successive dehalogenation reactions (PcpC). The intermediate produced is then cleaved by a dioxygenase (PcpA) and further metabolized (Cai and Xun 2002).
Under anaerobic conditions, PCP can serve as an electron acceptor for some Desulfitobacterium and Dehalococcoidesspecies. In each case however, complete reductive dechlorination of PCP to phenol was not observed. Instead, PCP dechlorination by Dehalococcoides resulted in the production of a mixture of dichloro- and monochlorophenols. Likewise, Desulfitobacterium strain PCP-1 dechlorinates PCP to 3-chlorophenol but other Desulfitobacterium species are only capable of ortho-dechlorination. Thus the net production of lesser chlorinated phenol must be considered when evaluating reductive dechlorination as a mechanism for PCP biodegradation.