putida [13, 33]. However, we found that only 29 nucleotides are present in the noncoding regions between benK and catB in A1501, suggesting AZD4547 that the promoter region of the catBC operon overlaps with the coding region of the benK gene. The promoter region of the catBC operon from A1501 shows very low similarity to those of the three other Pseudomonas strains, notably the lack of the typical binding site for CatR present in the catB promoter region of other Pseudomonas strains (Figure 6C). Although a catR orthologue could not be identified in
A1501, quantitative real-time PCR experiments indicated that RepSox concentration benzoate has the strongest induction effect on expression of the catBC operon (Figure 6D). Since benzoate induces expression of catB in the benR mutant background and this mutant is unable to metabolize benzoate, we proposed that induction of the catBC expression is not due to the production of benzoate metabolites, such as cis,cis-muconate. AZD5363 As reported in P. putida, induction of the catBC operon requires cis,cis-muconate, an intermediate of benzoate degradation, and CatR, a well-studied activator in the β-ketoadipate pathway . However, benzoate itself has a significant induction effect on expression of the catBC
operon in A1501, strongly suggesting the existence of an uncharacterized regulatory mechanism. Benzoate degradation in A1501 is subject to carbon catabolite repression In Pseudomonas and Acinetobacter strains, the Crc global regulator controls the
expression of genes involved in benzoate degradation when other preferred carbon sources Resveratrol are present in the culture medium [16, 17]. Based on sequence comparison, we found a Crc-like protein in the A1501 genome (Figure 1A). The A1501 Crc-like protein shows highest amino acid identity with P. aeruginosa Crc (86%), whereas relatively low amino acid identity (only 38%) is observed between A1501 and A. baylyi Crc proteins. Benzoate degradation by A1501 involves the oxidation of benzoate into catechol in a two-step process catalyzed by BenABC and BenD, two peripheral pathway enzymes of the catechol pathway. The catechol aromatic ring is converted by the action of CatA, CatB and CatC to cis,cis-muconate, and then to β-ketoadipate-enol-lactone, which is transformed into acetyl-CoA and succinyl-CoA by PcaD, PcaIJ, and PcaF from the β-ketoadipate pathway. Therefore, the benA, catB, and pcaD genes were selected for further analysis. In the presence of the inducer benzoate, highly significant differences in expression were observed, depending on the nature of the non-inducing carbon source (Figure 7). The expression of the three selected genes was most efficiently induced by benzoate when cells were grown on lactate and succinate alone, but was decreased significantly when the carbon source was glucose or acetate (Figure 8).