Anaerobic degradation of m-cresol by Desulfobacterium cetonicum is initiated by formation of 3-hydroxybenzylsuccinate

Abstract

The anaerobic bacterium Desulfobacterium cetonicum oxidized m-cresol completely with sulfate as electron acceptor. During growth, 3-hydroxybenzylsuccinate (identified by gas chromatography/mass spectroscopy and by comparison of high-performance liquid chromatography retention time and UV spectrum with a chemically synthesized reference compound) accumulated in the medium. This finding indicates that the methyl group of m-cresol is activated by addition to fumarate as in the case of anaerobic toluene metabolism. In cell-free extracts of D. cetonicum, the formation of 3-hydroxybenzylsuccinate from m-cresol and fumarate was detected at an activity of 0.5 nmol min(-1) (mg protein)(-1). This reaction depended strictly on anoxic assay conditions. Treatment with air resulted in a complete loss of activity; however, some activity could be recovered after restoring anoxic conditions. The activity was slightly membrane-associated. 3-Hydroxybenzylsuccinate was degraded via CoA thioesterification and further oxidation to 3-hydroxybenzoyl-CoA as subsequent steps in the degradation pathway.