Organization and Regulation of Pentachlorophenol-Degrading Genes in Sphingobium chlorophenolicum ATCC 39723

Abstract

ABSTRACT The first three enzymes of the pentachlorophenol (PCP) degradation pathway in Sphingobium chlorophenolicum (formerly Sphingomonas chlorophenolica ) ATCC 39723 have been characterized, and the corresponding genes, pcpA , pcpB , and pcpC , have been individually cloned and sequenced. To search for new genes involved in PCP degradation and map the physical locations of the pcp genes, a 24-kb fragment containing pcpA and pcpC was completely sequenced. A putative LysR-type transcriptional regulator gene, pcpM , and a maleylacetate reductase gene, pcpE , were identified upstream of pcpA. pcpE was found to play a role in PCP degradation. pcpB was not found on the 24-kb fragment. The four gene products PcpB, PcpC, PcpA, and PcpE were responsible for the metabolism of PCP to 3-oxoadipate in ATCC 39723, and inactivational mutation of each gene disrupted the degradation pathway. The organization of the pcp genes is unusual because the four PCP-degrading genes, pcpA , pcpB , pcpC , and pcpE , were found to be located at four discrete locations. Two hypothetical LysR-type regulator genes, pcpM and pcpR, have been identified; pcpM was not required, but pcpR was essential for the induction of pcpB , pcpA , and pcpE . The coinducers of PcpR were PCP and other polychlorinated phenols. The expression of pcpC was constitutive. Thus, the organization and regulation of the genes involved in PCP degradation to 3-oxoadipate were documented.