A meta cleavage pathway for 4-chlorobenzoate, an intermediate in the metabolism of 4-chlorobiphenyl by Pseudomonas cepacia P166

Abstract

Bacterial degradation of biphenyl and polychlorinated biphenyls proceeds by a well-studied pathway which produces benzoate and 2-hydroxypent-2,4- dienoate (or, in the case of polychlorinated biphenyls, the chlorinated derivatives of these compounds). Pseudomonas cepacia P166 utilizes 4- chlorobiphenyl for growth and produces 4-chlorobenzoate as a central intermediate. In this study we found that strain P166 further transforms 4- chlorobenzoate to 4-chlorocatechol, which is mineralized by a meta cleavage pathway. Key metabolites which we identified include the meta cleavage product (5-chloro-2-hydroxymuconic semialdehyde), 5-chloro-2- hydroxymuconate, 5-chloro-2-oxopent-4-enoate, 5-chloro-4-hydroxy-2- oxopentanoate, and chloroacetate. Chloroacetate accumulated transiently, and slow but stoichiometric dehalogenation was observed.