title: [Escherichia coli K-12 mutants with increased resistance to ionizing radiation. V. The effect of mutations on spontaneous and radiation mutagenesis].
abstract: The frequencies of spontaneous mutations (reversions his-4----His+ and forward mutations to rifampicin-, nalidixic acid- or valine-resistance) in radiation-resistant mutants Gamr444 and Gamr445 are much lower than in the wild-type strain AB1157. His+ revertants and rifampicin-resistant mutants Rifr are induced by low doses of gamma-rays more efficiently than in the wild-type. Low doses of UV light only enhanced mutagenic activity in Gamr strains for induction of His+ reversions but not for Rifr mutations. For the wild-type strain the frequencies of His+ and Rifr mutations increase proportionally to the square of dose both of UV light and gamma-rays. For the most radioresistant Gamr444 mutant the frequencies of UV- and gamma-rays-induced Rifr mutations and of gamma-rays-induced reversions increase linearly with the dose. Possible reasons for these anomalies of radiation-induced mutagenesis in Gamr mutants are discussed.
mesh_terms: D004260:DNA Repair / Q000528:radiation effects; D004269:DNA, Bacterial / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000235:genetics / Q000528:radiation effects*; D005720:Gamma Rays; D009154:Mutation; D011836:Radiation Tolerance; D014466:Ultraviolet Rays
chemical_list: D004269:DNA, Bacterial
vernacular_title: Mutanty Escherchia coli K-12 s povyshennoĭ ustoĭchivost'iu k ioniziruiushcheĭ radiatsii. Soobshchenie V. Vliianie mutatsiĭ na spontannyĭ i radiatsionnyĭ mutagenez.