Genetic characterization of 4-cresol catabolism in Corynebacterium glutamicum

Corynebacterium glutamicum uses 4-cresol as sole carbon source for growth. Protocatechuate 3,4-dioxygenase activity had been detected when C. glutamicum was grown with 4-cresol. In this work, we found that 4-cresol was catabolized via 4-hydroxybenzoate and protocatechuate as intermediate metabolites, and a genetic cluster called cre (designated for 4-cresol, creABCDEFGHIR, tagged as ncgl0521-ncgl0531 in NCBI) was identified. The cre gene cluster comprises of 11 genes, and six of them were experimentally confirmed to be involving in 4-cresol catabolism. The genes creD, creE, and creJ were involved in oxidation of 4-cresol into 4-hydroxybenzyl alcohol. The creD encoded a protein showing Mg(2+)-dependent phosphohydrolase activity. The genes creE, creF, creJ encoded a putative P450 system. The creG encoded a NAD(+)-dependent dehydrogenase and catalyzed 4-hydroxybenzyl alcohol to 4-hydroxybenzaldehyde. Two other genes creH and creI were involved in conversion of 4-hydroxybenzyl alcohol to 4-hydroxybenzoate, but their catalytic function is still unknown. Similar genetic clusters with high DNA sequence identity were identified in Arthrobacter and additional Corynebacterium species, suggesting that this genetic organization for 4-cresol catabolism might be more widely distributed in Gram-positive bacteria.