A novel bioluminescent bacterial biosensor using the highly specific oxidative stress-inducible pgi gene

A new oxidative stress-responsive bacterial biosensor was constructed using the promoter of the pgi gene fused to the luxCDABE reporter. This strain (PGRFM) responded in a dose-dependent manner to methyl viologen (MV), a model redox chemical that results in oxidative stress. The responses of strain PGRFM to redox chemicals was strongly dependent on the available carbon source. For example, when the strain was grown under nutrient-limited conditions in the presence of glucose or gluconate it was capable of responding to low MV concentrations (0.6-19.3 ppm), whereas the same cells grown in LB (a nutrient rich media) only responded to higher concentrations (4.9-625 ppm). This allowed us to select PGRFM's growth conditions and extend the range of concentrations at which a stress-inducing chemical could be detected. Further, strain PGRFM responded to structural analogs of MV (i.e., ethyl and benzyl viologen), demonstrating that this strain is responsive to the presence of superoxide radicals, regardless of the chemical by which they are generated. Strain PGRFM's response patterns to these analogs were distinct from each other, which determined their strength to induce oxidative stress. As well, a significant induction was seen when this strain was exposed to hydrogen peroxide, illustrating that strain PGRFM is responsive in the presence of both the superoxide (O₂{radical dot}^-) and hydroxyl (OH{radical dot}) radicals.