Synergistic Killing of Escherichia Coli K-12 by UV (254nm) and H₂O₂

Summary

Prior UV irradiation strongly increased the sensitivity to H₂O₂ of wild-type E. coli K-12 cells. This synergistic lethal interaction was also observed to a reduced extent in a polA mutant but was absent in uvrAuvrArecA and xthA mutants. In a recA mutant an antagonistic effect was observed. Prior H₂O₂ treatment did not sensitize the wild-type cells to UV irradiation. Alkaline and neutral sucrose gradient analysis, as well as DNA degradation studies, demonstrated that the synergism is due to the production of DNA double-strand breaks and a block of their repair. The possible mechanism of induction of such lesions is discussed.