Figure 6.
Co-consumption of benzoate and POB. (A) Schematic depicting regulation and metabolism of POB and benzoate. These two growth substrates, which enter the PCA and catechol branches of the β-ketoadipate pathway, respectively, are funneled to central carbon metabolism. POB uptake and degradation are encoded by the pob and pca genes, whereas benzoate uptake and degradation are encoded by the ben and cat genes. Benzoate consumption requires two transcriptional regulators (BenM and CatM) that, in response to muconate, activate ben- and cat-gene transcription. These regulators also bind upstream of the pcaIJFBDKCHG operon in a muconate-dependent fashion at a site that should repress transcription (33). Consumption patterns are shown for: (B) the wild-type strain, ADP1, (C) a strain (ACN2469) where the transporter gene pcaK is transcribed constitutively from a synthetic promoter (D5H6), (D) a strain (ACN2596) where the binding site for BenM/CatM upstream of the pca operon has been scrambled to prevent binding of these regulators and (E) a strain (ACN2569) where benM has been inactivated, catM has been deleted and where the genes for benzoate degradation, which are normally activated by BenM and CatM, are under constitutive expression. In ACN2569 the ben genes are controlled by a promoter mutation (PbenA5147) and the cat genes are transcribed from synthetic promoters (T5 for catA and F6C5 for catBCIJFD). Data shown are average of at least three biological replicates. Error bars represent standard deviation.