As shown in Figure 2, the gene arrangement of the ben, cat, and pca clusters differs between different bacteria. Apparently, various

DNA rearrangements have occurred during its evolution in each particular host. Furthermore, we observed the lack of check details the catR and pcaK genes, a distinguishing feature of the catabolic gene organization in A1501, suggesting that gene deletion events responsible for the loss of the two genes have occurred over a long period of evolution. In most cases, the complex regulatory circuits involving the two sets of transcriptional regulators, BenR/BenM and CatR/CatM, have evolved to allow optimal expression of catabolic genes [39, 40]. Unlike P. putida in which the transcription of the catBC operon requires CatR and cis,cis-muconate [32], we could not identify a catR orthologue or a consensus sequence typical of CatR-dependent promoters in A1501. In particular, benzoate, but not cis,cis-muconate, has a significant induction effect on the expression of the catBC operon in A1501. Therefore, we propose that an uncharacterized Small Molecule Compound Library regulatory mechanism might be involved in the regulation of the β-ketoadipate pathway in A1501, but this hypothesis requires further Belnacasan investigation. A1501 contains all of the enzymes involved in the 4-hydroxybenzoate degradation pathway. However,

this strain shows extremely poor growth on 4-hydroxybenzoate as the sole carbon source. A plausible explanation for this observation is due to the lack of PcaK, a 4-hydroxybenzoate transporter, thereby leaving A1501 unable to metabolize 4-hydroxybenzoate efficiently. In most cases, the pcaK mutation had a negative effect on bacterial 4-hydroxybenzoate uptake and growth. For example, mutants blocked in 4-hydroxybenzoate transport have been identified in two biovars of Rhizobium leguminosarum [41]. Growth of these mutants was completely blocked when cultured on 4-hydroxybenzoate. By contrast, growth of the P. putida pcaK mutant was not significantly impaired on 4-hydroxybenzoate at neutral pH [30]. Furthermore, repression of 4-hydroxybenzoate transport and degradation by benzoate has been reported in P. putida [42]. Unexpectedly, our results indicate that low concentrations of 4-hydroxybenzoate

significantly enhance the ability of A1501 to degrade benzoate, potentially Temsirolimus due to 4-hydroxybenzoate-mediated induction of enzymes, such as PcaD, required for dissimilation of benzoate by the β-ketoadipate pathway. Pesticides and industrial wastes often contain aromatic constituents, including many that are toxic to living organisms. The degradation of aromatic compound mixtures has recently received a great deal of attention. To our knowledge, this is the first report of enhanced benzoate degradation by 4-hydroxybenzoate, highlighting its potential physiological significance. The metabolic capacity for utilizing different aromatic compounds as carbon or energy sources confers a selective advantage, notably for exposure to a mixture of aromatic compounds.