Detection and classification of oxidative damaging stresses using recombinant bioluminescent bacteria harboring sodA::, pqi::, and katG::luxCDABE fusions

A recombinant bioluminescent Escherichia coli DH5α strain, EBJM1 (pqi-5::luxCDABE), was constructed in this study by fusing the promoter for the pqi-5 gene, which is a member of the soxRS regulon but with an unknown function, to the Vibrio fisheri luxCDABE operon within plasmid pUCD615. The soxRS-dependent activation of the pqi-5 promoter was seen when this strain was exposed to paraquat, a superoxide radical-generating agent. The different response patterns and sensitivities of strain EBJM1 to several oxidative chemicals, including hydrogen peroxide, cadmium chloride, and paraquat, were then compared with the responses from strains EBHJ1 (sodA::luxCDABE), which is strongly induced by redox-cycling agents, and EB2511 (katG::luxCDABE), which is sensitive to hydrogen peroxide. It was found that the responses from the pqi-5-, sodA- and katG-based strains were distinct according to the chemical being tested. In particular, the responses from the pqi-5 and sodA strains, which have the same transcriptional factor, were most responsive when the superoxide radical was produced. The pqi-5 strain, EBJM1, was also responsive to the production of nitrate. This comparison provided information on the potential mechanisms of the various toxicants examined and known responses of the promoters to specific radicals. Furthermore, using these three strains, cellular damage that is caused by oxidative radicals can be classified using the distinct differences in the responses between the pqi-5, sodA, and katG promoters.