Microbial Insights

Detect and quantify bacteria responsible for biodegradation of PCP

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.  Although used as a biocide, PCP is susceptible to biodegradation.  Under aerobic conditions, PCP biodegradation is initiated by a PCP 4-monooxygenase (PcpB) followed by two successive dehalogenation reactions (PcpC).  The intermediate produced is then cleaved by a dioxygenase (PcpA) and further metabolized.  Under anaerobic conditions, PCP can serve as an electron acceptor for some Desulfitobacterium and Dehalococcoides species.  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.

CENSUS Targets for Aerobic PCP

Pentachlorophenol Monooxygenases (qPCP): CENSUS assay specifically targeting oxygenase genes encoding the enzymes responsible for initial oxidation of PCP and aromatic ring cleavage.

CENSUS Targets for Anaerobic PCP

Desulfitobacterium (qDSB): Dechlorination activity varies between Desulfitobacterium strains, however, many appear capable of reductive dechlorination of PCP (at ortho positions).  Moreover,  Desulfitobacterium strain PCP-1 exhibits a broader substrate range and has been shown to reduce PCP to 3-chlorophenol.

Dehalococcoides (qDHC): Although most widely studied for the ability to utilized chlorinated ethenes as electron acceptors, some Dehalococcoides strains are capable of reductive dechlorination of PCP and other chlorinated phenols.

References

Cai, M. and L. Xun.  2002.  “Organization and regulation of pentachlorophenol-degrading genes in Spingobium chlorophenolicum ATCC 39723”.  Journal of Bacteriology 184(17): 4672-4680.

Bouchard, B., R. Beaudet, R. Villemur, G. McSween, F. Lepine, and J.-G. Bisaillon.  1996.  “Isolation and characterization of Desulfitobacterium frappieri sp. nov., an anerobic bacterium which reductively dechlorinates pentachlorophenol to 3-chlorophenol”.  International Journal of Systematic Bacteriology.  46(4): 1010-1015.

Adrian, L., S.K. Hansen, J.M. Fung, H. Gorisch, and S.H. Zinder.  2007.  “Growth of Dehalococcoides strains with chlorophenols as electron acceptors”.  Environmental Science & Technology. 41(7): 2318-2323.