Fluorescence and bioluminescence reporter functions in genetically modified bacterial sensor strains

Genetically modified bacteria, engineered to generate a quantifiable signal in response to pre-determined sets of environmental conditions, may serve as combined sensing/reporting elements in whole-cell biosensors. We have compared two of the several available reporter genes in such cells: green fluorescent proteins (GFPs) (Aquorea victoria gfp) and bioluminescence (Vibrio fischeri luxCDABE) genes, fused to either SOS (recA) or heat shock (grpE) promoters. In both cases, bacterial bioluminescence allowed faster and more sensitive detection of the model toxicants; the fluorescent reporter proteins were much more stable, and following long-term exposure allowed detection at levels similar to that of the bioluminescent sensors. From the two green fluorescent proteins tested, enhanced GFP (EGFP) displayed a more rapid response and higher signal intensity than GFPuv. To combine the advantages of both reporter functions, representatives of both types were jointly encapsulated in a sol–gel matrix and immobilized onto a glass surface, to generate a bioluminescent toxicity and a fluorescent genotoxicity sensor. The dual-function sensor detected both toxic and genotoxic model compounds with no interference from the co-immobilized member.