Aerobic degradation of tetrachloroethylene by toluene-o-xylene monooxygenase of Pseudomonas stutzeri OX1

Tetrachloroethylene (PCE) is thought to have no natural source, so it is one of the most difficult contaminants to degrade biologically. This common groundwater pollutant was thought completely non-biodegradable in the presence of oxygen. Here we report that the wastewater bacterium Pseudomonas stutzeri OX1 degrades aerobically 0.56 mu mol of 2.0 mu mol PCE in 21 h (V-max approximate to 2.5 nmol min(-1) mg(-1) protein and K-M approximate to 34 mu M). These results were corroborated by the generation of 0.48 mu mol of the degradation product, chloride ions. This degradation was confirmed to be a result of expression of toluene-o-xylene monooxygenase (ToMO) by P. stutzeri OX1, since cloning and expressing this enzyme in Escherichia coli led to the aerobic degradation of 0.19 mu mol of 2.0 mu mol PCE and the generation of stoichiometric amounts of chloride. In addition, PCE induces formation of ToMO, which leads to its own degradation in P. stutzeri OX1. Degradation intermediates reduce the growth rate of this strain by 27%.