title: Plasmid (pKM101)-mediated Weigle reactivation in Escherichia coli K12 and Salmonella typhimurium LT2: genetic dependence, kinetics of induction, and effect of chloramphenicol.
abstract: In Escherichia coli K12 the reactivation of UV-irradiated phage in UV-irradiated cells (Weigle reactivation) is inhibited if the protein synthesis inhibitor chloramphenicol is present during the post-irradiation incubation. In contrast, in E. coli K12 or Salmonella typhimurium LT2 containing the plasmid pKM101 the kinetics of the W-reactivation response were not affected by chloramphenicol. Under the conditions used, protein synthesis was greater than 99% inhibited and no preferential synthesis of plasmid-coded proteins was apparent in the residual protein synthesis. This increased capacity to reactivate irradiated phage decayed over 2 h if the cells were allowed to grow but was relatively stable if they were incubated in 10 mM MgSO4. Whereas the capacity of UV-irradiated bacteria with or without pKM101 to carry out W-reactivation had largely decayed by the end of a 2 h post-irradiation incubation in minimal-glucose with chloramphenicol, the capacity to synthesize high levels of the recA protein had not. Post-irradiation treatment with chloramphenicol did not abolish the UV-protective effect of pKM101 or R46. pKM101-mediated W-reactivation is recA+-dependent in S. typhimurium and recA+ lexA+-dependent in E. coli K-12. The inefficiency of S. typhimurium LT2 relative to E. coli in carrying out W-reactivation is not due to the presence of the cryptic plasmid in the LT2 strains. Two possible models are discussed.
mesh_terms: D002701:Chloramphenicol / Q000494:pharmacology*; D004260:DNA Repair / Q000528:radiation effects*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D007700:Kinetics; D010957:Plasmids / Q000187:drug effects; D011836:Radiation Tolerance; D012486:Salmonella typhimurium / Q000235:genetics*; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial; D002701:Chloramphenicol