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 furthe r insight into the phylogenetic relationships of PCP-degrading bacteri a, we examined four strains: Arthuobacter sp. strain ATCC 33790, Flavo bacterium sp. strain ATCC 39723, Pseudomonas sp. strain SR3, and Sphin gomonas sp. strain RA2. These organisms were isolated from different g eographical locations and all of them degrade high concentrations (100 -200 mg/L) of PCP. Southern blot analyses determined that these bacter ia all harbour DNA that encodes similar, if not identical, genes invol ved in PCP degradation. Comparison of the 16S rRNA nucleotide sequence s 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 st rains 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 th e PCP degradative pathway.