Gene cluster cehBDEF is responsible for the conversion of 1,2-dihydroxynaphthalene to salicylate in Rhizobium sp. strain X9

Rhizobium sp. strain X9 was able to degrade 1-naphthol via 1,2-dihydroxynaphthalene (1,2-DHN), salicylate and gentisate. We have identified the two component hydroxylase gene cehC1C2 (responsible for the conversion of 1-naphthol to 1,2-DHN) and genes cehG, cehH, and cehI involved in CoA dependent hydroxylation reaction (conversion of salicylate to gentisate). However, the other genes involved in the degradation pathway (from 1,2-DHN to salicylate) have not been identified yet. In this study, the cehBDEF gene cluster organized in the same operon was identified to be involved in the degradation of 1,2-DHN to salicylate. CehB was a novel 1,2-DHN dioxygenase that catalyzes 1,2-DHN to 2-hydroxychromene-2-carboxylate (HCCA), sharing only 28.2% amino acid identity with catechol 2,3-dioxygenase (P31003). CehD, cehE and CehF were conserved with the previously reported corresponding enzymes in 1-naphthol degradation (identity >60%). They are responsible for the successive conversion of HCCA to salicylate. The current study fills in the gap of the genes involved in the 1-naphthol degradation in strain X9.