Stress specific Escherichia coli biosensors based on gene promoters for toxicity monitoring

Target specific biosensor Escherichia coli strains have been engineered for studying the stress action. Four different recombinant E. coli biosensors were constructed by fusing one promoter each of ung, rseA, ibpA, and yggX gene in pET-21a::lacZ system, which contains very effective color-readout sensing system. The responses of four bacteria sensor strains, UNGLacZ, RSEALacZ, IBPALacZ, and YGGXLacZ, have been characterized under treatment with mitomycin C (MMC), phenol, ethanol and hydrogen peroxide (H2O2), respectively. UNGLacZ responded strongly only to MMC (DNA damaging chemical), whereas no response has been observed with phenol, which is a membrane damage chemical. However, RSEALacZ gave significant response with phenol. In addition, ethanol and hydrogen peroxide caused dose-dependent induction from IBPALacZ and YGGXLacZ, respectively. Thus, the results of the present study demonstrate that four bacterial strains show significant and different responses based on various stress defense mechanisms, which these genes originally possessed in E. coli. The four bacterial biosensors can be potentially used in environmental Point-of-Care Testing (ePOCT) leading to quick, easy and early detection of toxic contaminants locally as well as resulting in real-time measurements.