Mutagenicity induced by UVC in Escherichia coli cells: reactive oxygen species involvement.

AbstractWe previously demonstrated that reactive oxygen species (ROS) could be involved in the DNA damage induced by ultraviolet-C (UVC). In this study, we evaluated singlet oxygen (1O2) involvement in UVC-induced mutagenesis in Escherichia coli cells. First, we found that treatment with sodium azide, an 1O2 chelator, protected cells against UVC-induced lethality. The survival assay showed that the fpg mutant was more resistant to UVC lethality than the wild-type strain. The rifampicin mutagenesis assay showed that UVC mutagenesis was inhibited five times more in cells treated with sodium azide, and stimulated 20% more fpg mutant. These results suggest that 1O2 plays a predominant role in UVC-induced mutagenesis. 1O2 generates a specific mutagenic lesion, 8-oxoG, which is repaired by Fpg protein. This lesion was measured by GC–TA reversion in the CC104 strain, its fpg mutant (BH540), and both CC104 and BH540 transformed with the plasmid pFPG (overexpression of Fpg protein). This assay showed that mutagene...