Tetrachloroethylene, trichloroethylene, and chlorinated phenols induce toluene-o-xylene monooxygenase activity in Pseudomonas stutzeri OX1
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Pseudomonas stutzeri OX1 naphthalene-oxidation activity is induced 3.0-fold by tetrachloroethylene (PCE) and 3.1-fold by trichloroethylene (TCE) at 100 µM. With the mutant P. stutzeri M1, which does not express toluene-o-xylene monooxygenase (ToMO, product of the tou operon), no naphthalene-oxidation activity induction by PCE and TCE was found; hence, PCE and TCE induce ToMO of P. stutzeri OX1. The chlorinated phenols 2-, 3-, and 4-chlorophenol induced ToMO expression 0.58-, 0.23- and 0.37-fold, respectively, compared to the direct inducer of the pathway, o-cresol. Using P. putida PaW340 (pPP4062, pFP3028), which has the tou promoter fused to the reporter catechol-2,3-dioxygenase, and the regulator gene touR, it was determined that the tou promoter was induced directly 5.7-, 7.1-, and 5.1-fold for 2-, 3-, and 4-chlorophenol, respectively (compared to an 8.8-fold induction with o-cresol). In addition, it was found that TCE and PCE do not directly induce the tou pathway and that components other than the tou structural and regulatory genes are necessary for induction. Gas chromatography results also showed that 100 µM TCE induced its own degradation (8–9%) in 16 h in P. stutzeri OX1, and all of the stoichiometric chloride from the degraded TCE was detected in solution.
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