Sensitivities and gene-expressions of Escherichia coli mutants deficient in DNA repair and reactive oxygen species scavenging capacity exposed to natural sunlight.

Sensitivities to sunlight of Escherichia coli mutants deficient in DNA repair capacities such as excision and recombination repair and their wild-type strain were compared. Higher sensitivities to sunlight were clearly observed in the mutant than wild-type strain, indicating that exposure to sunlight induces DNA damage which is repaired by DNA repair mechanisms. In order to assess the role of generation of reactive oxygen species (ROS) in DNA damage induced by exposure to natural sunlight, the kat-sod assay was performed using E. coli mutant strains deficient in ROS scavenging enzymes such as superoxide dismutase and/or catalase. Natural sunlight induced a significant generation of ROS, suggesting a possibility that sunlight induced ROS may be involved in DNA damage in bacterial cells.