摘要：Escherichia coli mutants which lack defence systems against such active oxygen forms as OxyR (Δ oxyR ), superoxide dismutase (SOD) ( sodA and sodB ) and catalase ( katE and katG ) are sensitive to UV-A lethality under aerobic conditions, whereas OxyR- and SOD-mutants have resistance under anaerobic conditions and in the presence of sodium azide (NaN 3 ) during irradiation. UV-A induces lipid peroxidation in the Δ oxyR mutant, which is suppressed by NaN 3 . These results suggest that UV-A generates 1 O 2 or the hydroxyl radical to produce lipid peroxides intracellularly in the Δ oxyR mutant and that O 2 - stress may be generated in the sodAB mutant after 8 hr of exposure to UV-A. The sensitivities of such DNA repair-deficient mutants as recA ind- and uvrA to UV-A also were examined and compared. These mutants are sensitive to UV-A lethality under aerobic conditions but show only slight resistance under anaerobic conditions or in the presence of NaN 3 during irradiation. We conclude that NaN 3 protects these mutant cells from oxygen-dependent UV-A lethality.
