Post‐UV DNA Synthesis in Escherichia coli TK501 umuC uvrB Carrying Plasmids that Protect Against, or Sensitize to, UV

Abstract

Many bacterial plasmids encode error-prone (mutagenic) DNA repair. Some antibacterial drugs, such as the quinolones, damage DNA and induce repair, and the presence of such plasmids may therefore increase clinical mutation frequency to drug resistance. Plasmid R46, which increases mutation frequency and protects strains of Escherichia coli against DNA damage induced by ultraviolet light (UV), together with plasmids R391 and pYD1, which increase mutation frequency, but sensitize to UV, and RP4, which does not affect post-UV survival, were tested in E. coli TK501 umuC uvrB for their effect on DNA synthesis after UV exposure. Synthesis recovered rapidly in the strain containing R46 compared to the plasmid-negative and RP4-containing controls, whereas in the R391 and pYD1-containing strains it remained lower than in controls for up to five hours. Both R46 and R391 carry genes that are homologues of chromosomal error-prone repair umuDC genes, and the data presented in this paper suggest that variation in the control of repair gene expression may account for the different plasmid-encoded UV phenotypes.