The Regulation of <i>para</i>-Nitrophenol Degradation in <i>Pseudomonas putida</i> DLL-E4

<div><p><i>Pseudomonas putida</i> DLL-E4 can efficiently degrade <i>para</i>-nitrophenol and its intermediate metabolite hydroquinone. The regulation of <i>para</i>-nitrophenol degradation was studied, and PNP induced a global change in the transcriptome of <i>P</i>. <i>putida</i> DLL-E4. When grown on PNP, the wild-type strain exhibited significant downregulation of 2912 genes and upregulation of 845 genes, whereas 2927 genes were downregulated and 891 genes upregulated in a <i>pnpR</i>-deleted strain. Genes related to two non-coding RNAs (<i>ins1</i> and <i>ins2</i>), <i>para</i>-nitrophenol metabolism, the tricarboxylic acid cycle, the outer membrane porin OprB, glucose dehydrogenase Gcd, and carbon catabolite repression were significantly upregulated when cells were grown on <i>para</i>-nitrophenol plus glucose. <i>pnpA</i>, <i>pnpR</i>, <i>pnpC1C2DECX1X2</i>, and <i>pnpR1</i> are key genes in <i>para</i>-nitrophenol degradation, whereas <i>pnpAb</i> and <i>pnpC1bC2bDbEbCbX1bX2b</i> have lost the ability to degrade <i>para</i>-nitrophenol. Multiple components including transcriptional regulators and other unknown factors regulate <i>para</i>-nitrophenol degradation, and the transcriptional regulation of <i>para</i>-nitrophenol degradation is complex. Glucose utilization was enhanced at early stages of <i>para</i>-nitrophenol supplementation. However, it was inhibited after the total consumption of <i>para</i>-nitrophenol. The addition of glucose led to a significant enhancement in <i>para</i>-nitrophenol degradation and up-regulation in the expression of genes involved in <i>para</i>-nitrophenol degradation and carbon catabolite repression (CCR). It seemed that <i>para</i>-nitrophenol degradation can be regulated by CCR, and relief of CCR might contribute to enhanced <i>para</i>-nitrophenol degradation. In brief, the regulation of <i>para</i>-nitrophenol degradation seems to be controlled by multiple factors and requires further study.</p>