The promoter of nrdA gene which is related with DNA synthesis was used to construct a DNA damage sensitive biosensor. A recombinant bioluminescent E. coli strain, BBTNrdA, harboring a plasmid with the nrdA promoter fused to the luxCDABE operon, was successfully constructed. Its response to various chemicals including genotoxic chemicals substantiates it as a DNA damage biosensor. In characterization, three different classes of toxicants were used: DNA damaging chemicals, oxidative stress chemicals, and phenolics. BBTNrdA only responded strongly to DNA damaging chemicals, such as nalidixic acid (NDA), mitomycin C (MMC), 1-methyl-1-nitroso-N-methylguanidine (MNNG), and 4-nitroquinoline N-oxide (4-NQO). In contrast, there were no responses from the oxidative stress chemicals and phenolics, except from hydrogen peroxide (H2O2) which is known to cause DNA damage indirectly. Therefore, the results of the study demonstrate that BBTNrdA can be used as a DNA damage biosensor.
Keywords: DNA damage response; ribonucleoside diphosphate reductase.