FIG. 9.

Metabolic reactions and clusters of genes involved in (A) the catabolism of phenol to 4-hydroxybenzoate, (B) reductive dehydroxylation of 4-hydroxybenzoyl-CoA to benzoyl-CoA, and (C) metabolism of 3-hydroxybenzoate by T. aromatica, “A. aromaticum” (Azoarcus sp. strain EbN1), G. metallireducens, and M. magneticum. In panel A, orfs 1, 2, and 3 encode proteins 1, 2, and 3, the components of phenylphosphate synthase, which catalyzes the phosphorylation of phenol to phenylphosphate. orfs 4, 5, 6, and 12 encode subunits α, δ, β, and γ of phenylphosphate carboxylase, which catalyzes the carboxylation of phenylphosphate to 4-hydroxybenzoate and releases phosphate. In panel B, HcrA, HcrB, and HcrC are three subunits of 4-hydroxybenzoyl-CoA reductase, and the open arrows indicate a regulatory protein belonging to the MarR family. In panel C, the genes for 3-hydroxybenzoate-CoA ligase (3HBCL) and other open reading frames are shown. The annotation of 3HBCL in “A. aromaticum” and M. magneticum is tentative but is supported by the similar flanking genes and by the high e value compared with the Thauera enzyme. orfs 1 and 3 encode putative alcohol dehydrogenases. orf 4 is similar to the acyl-CoA dehydrogenase gene, and the orf 6 translated product is a putative hydrolase. The function of orf 2 is not known. The gray arrows indicate the open reading frames that were not found in the T. aromatica gene cluster.