Toluene-degrading bacteria are chemotactic towards the environmental pollutants benzene, toluene, and trichloroethylene

The bioremediation of polluted groundwater and toxic waste sites requires t hat bacteria come into close physical contact with pollutants, This can be accomplished by chemotaxis. Five motile strains of bacteria that use five d ifferent pathways to degrade toluene were tested for their ability to detec t and swim towards this pollutant, Three of the five strains (Pseudomonas p utida F1, Ralstonia pickettii PKO1, and Burkholderia cepacia G4) were attra cted to toluene, In each case, the response was dependent on induction by g rowth with toluene, Pseudomonas mendocina KR1 and P. putina PaW15 did not s how a convincing response. The chemotactic responses of P, putida F1 to a v ariety of toxic aromatic hydrocarbons and chlorinated aliphatic compounds w ere examined. Compounds that are growth substrates for P, putida F1, includ ing benzene and ethylbenzene, were chemoattractants. P. putina F1 was also attracted to trichloroethylene (TCE), which is not a growth substrate but i s dechlorinated and detoxified by P, putida F1, Mutant strains of P, putina F1 that do not oxidize toluene were attracted to toluene, indicating that toluene itself and not a metabolite was the compound detected. The two-comp onent response regulator pair TodS and TodT, which control expression of th e toluene degradation genes in P, putida F1, were required for the response . This demonstration that soil bacteria can sense and swim towards the toxi c compounds toluene, benzene, TCE, and related chemicals suggests that the introduction of chemotactic bacteria into selected polluted sites may accel erate bioremediation processes.