A dual-color bacterial reporter strain for the detection of toxic and genotoxic effects

To genetically engineer a bacterial whole cell dual-function toxicity/ genotoxicity bioreporter system, a plasmid was constructed containing two independent fusions of stress-responsive promoters (of the recA and grpE genes) to green and red fluorescent protein reporter genes, respectively. An Escherichia coli strain harboring this plasmid exhibited distinct green fluorescence in response to the presence of the SOS inducing agent nalidixic acid, and red fluorescence in reaction to ethanol. The different fluorescent responses, which exhibited little or no overlap, were quantified by microtiter plate fluorometry, confocal microscopy, and fluorescence emission spectroscopy. Mutations in lexA and rpoH, which affected the E. coli SOS and heat shock systems, respectively, abolished the green and red fluorescence. Similar constructs may serve as biological entities in future whole-cell toxicity/genotoxicity biosensor systems.