Kinetic analyses of trichloroethylene cometabolism by toluene-degrading bacteria harboring a tod homologous gene

We have previously constructed a bacterial library consisting of toluene-degrading bacteria isolated from soil, activated sludge, and trichloroethylene (TCE) waste. In the present study, the library was subjected to colony hybridization with todC1C2-encoding terminal oxygenase of a multicomponent enzyme that is responsible for the first oxidation of toluene, toluene dioxygenase (TDO). Three strains, A1071, IB5, and B6122, which showed positive signals with todC1C2 by the colony hybridization, were selected on the basis of results of a preliminary degradation assay for detail analyses of degradation kinetics of toluene and TCE. Their possession of the gene homologous to todC1, a large subunit of TDO of Pseudomonas putida F1, was confirmed by dot hybridization analysis using their chromosomal DNA extracts as templates. Results of degradation experiments using resting cells revealed the variety in TCE degradation ability among these strains; A1071 demonstrated degradation kinetics similar to the strain F1 while B6122 could not degrade TCE at all. The interaction between toluene and TCE on their degradation could be simply expressed by competitive inhibition.