Bioconversion of 2-hydroxy-6-oxo-6-(4'-chlorophenyl)hexa-2,4-dienoic acid, the meta-cleavage product of 4-chlorobiphenyl.

Bacterial conversion of 4-chlorobiphenyl (4-CB) usually proceeds through a pathway involving an initial oxidation of the unsubstituted ring in the 2,3 position followed by a 1,2 meta-cleavage. The meta-cleavage product (MCP) is converted through a single hydrolysis step into chlorobenzoic acid. However, several other acidic metabolites that were not expected as part of this pathway have already been described. In this paper, we used strains of Pseudomonas putida carrying cloned genes from Pseudomonas testosteroni B-356 that are involved in polychlorinated biphenyl (PCB) degradation to demonstrate that several acidic metabolites found in the culture media of various bacteria grown in the presence of 4-CB result from alternative novel bioconversion pathways of MCP. The degradation products of MCP through these pathways were identified as analogues with saturated or shorter side chains or as 4'-chlorophenyl-2-picolinic acid; pathways leading to their formation are proposed.