PCP degradation is mediated by closely related strains of the genus Sphingomonas

There have been numerous reports in the literature of diverse bacteria capable of degrading pentachlorophenol (PCP). In order to gain further insight into the phylogenetic relationships of PCP-degrading bacteria, we examined four strains: Arthrobacter sp. strain ATCC 33790, Flavobacterium sp. strain ATCC 39723, Pseudomonas sp. strain SR3, and Sphingomonas sp. strain RA2. These organisms were isolated from different geographical locations and all of them degrade high concentrations (100-200 mg/L) of PCP. Southern blot analyses determined that these bacteria all harbour DNA that encodes similar, if not identical, genes involved in PCP degradation. Comparison of the 16S rRNA nucleotide sequences revealed that these organisms were very closely related and, in fact, represent a monophyletic group. The 16S rRNA analyses together with fatty acid and sphingolipid analyses strongly suggest that the four strains are members of the genus Sphingomonas. The close relationship of the four organisms is supported by nucleotide sequence analysis data of the pcpB locus encoding PCP-4-monooxygenase, the first enzyme in the PCP degradative pathway.