Initiation of Anaerobic Degradation of p -Cresol by Formation of 4-Hydroxybenzylsuccinate in Desulfobacterium cetonicum

Abstract

ABSTRACT The anaerobic bacterium Desulfobacterium cetonicum oxidized p -cresol completely to CO 2 with sulfate as the electron acceptor. During growth, 4-hydroxybenzylsuccinate accumulated in the medium. This finding indicated that the methyl group of p -cresol is activated by addition to fumarate, analogous to anaerobic toluene, m -xylene, and m -cresol degradation. In cell extracts, the formation of 4-hydroxybenzylsuccinate from p -cresol and fumarate was detected at an initial rate of 0.57 nmol min −1 (mg of protein) −1 . This activity was specific for extracts of p -cresol-grown cells. 4-Hydroxybenzylsuccinate was degraded further to 4-hydroxybenzoyl-coenzyme A (CoA), most likely via β-oxidation. 4-Hydroxybenzoyl-CoA was reductively dehydroxylated to benzoyl-CoA. There was no evidence of degradation of p -cresol via methyl group oxidation by p -cresol-methylhydroxylase in this bacterium.