DEVELOPMENT AND TESTING OF A BACTERIAL BIOSENSOR FOR TOLUENE-BASED ENVIRONMENTAL CONTAMINANTS

A bacterial biosensor for benzene, toluene, and similar compounds has been constructed, characterized, and field tested on contaminated wate r and soil, The biosensor is based on a plasmid incorporating the tran scriptional activator xylR from the TOL plasmid of Pseudomonas putida mt-2, The XylR protein binds a subset of toluene-like compounds and ac tivates transcription at its promoter, P-u. A reporter plasmid was con structed by placing the luc gene for firefly luciferase under the cont rol of XylR and P-u. When Escherichia coli cells were transformed with this plasmid vector, luminescence from the cells was induced in the p resence of benzene, toluene, xylenes, and similar molecules, Accurate concentration dependencies of luminescence were obtained and exhibited K-1/2 values ranging from 39.0 +/- 3.8 mu M for 3-xylene to 2,690 +/- 160 mu M for 3-methylbenzylalcohol (means +/- standard deviations), T he luminescence response was specific for only toluene-like molecules that bind to and activate XylR. The biosensor cells were field tested on deep aquifer water, for which contaminant levels were known, and we re able to accurately detect toluene derivative contamination in this water, The biosensor cells were also shown to detect BETX (benzene, to luene, and xylene) contamination in soil samples, These results demons trate the capability of such a bacterial biosensor to accurately measu re environmental contaminants and suggest a potential for its inexpens ive application in field-ready assays.