The Organophosphate Degradation (opd) Island-borne Esterase-induced Metabolic Diversion in Escherichia coli and Its Influence on p-Nitrophenol Degradation

In previous studies of the organophosphate degradation gene cluster, we showed that expression of an open reading frame (orf306) present within the cluster in Escherichia coli allowed growth on p-nitrophenol (PNP) as sole carbon source. We have now shown that expression of orf306 in E. coli causes a dramatic up-regulation in genes coding for alternative carbon catabolism. The propionate, glyoxylate, and methylcitrate cycle pathway-specific enzymes are up-regulated along with hca (phenylpropionate) and mhp (hydroxyphenylpropionate) degradation operons. These hca and mhp operons play a key role in degradation of PNP, enabling E. coli to grow using it as sole carbon source. Supporting growth experiments, PNP degradation products entered central metabolic pathways and were incorporated into the carbon backbone. The protein and RNA samples isolated from E. coli (pSDP10) cells grown in 14C-labeled PNP indicated incorporation of 14C carbon, suggesting Orf306-dependent assimilation of PNP in E. coli cells. Background: Because of the mobile nature of the opd island, identical opd and orf306 sequences are found among soil bacteria. Results: In E. coli, Orf306 suppresses glycolysis and the TCA cycle and promotes up-regulation of alternate carbon catabolic operons. Conclusion: The up-regulated hca and mhp operons contribute to PNP-dependent growth of E. coli. Significance: Together with opd, orf306 contributes to the complete mineralization of OP residues.