大腸菌における紫外線と4NQOによる突然変異の用量率依存性

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  • DAI Hwa
    Department of Fundamental Radiology, Faculty of Medicine, Osaka University
  • ICHIKAWA-RYO Haruko
    Department of Fundamental Radiology, Faculty of Medicine, Osaka University
  • KONDO Sohei
    Department of Fundamental Radiology, Faculty of Medicine, Osaka University

書誌事項

タイトル別名
  • Dose-rate dependence of mutagenesis by ultraviolet radiation and 4-nitroquinoline 1-oxide in Escherichia coli.
  • 大腸菌における紫外線と4NQOによる突然変異の用量率依存性〔英文〕
  • ダイチョウキン ニ オケル シガイセン ト 4NQO ニヨル トツゼン ヘンイ

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説明

To study the dose-rate dependence of mutagenesis in Escherichia coli by ultraviolet radiation (UV) and UV-mimetic chemical, 4-nitroquinoline 1-oxide (4NQO), equal total doses of UV or 4NQO were given to bacteria at high dose- rates in single doses and at low dose-rates by continuous exposure or in fractionated doses during a 7 hr period of holding the cells in buffer. Yields of mutations to prototrophy in a repair-proficient strain greatly decreased after low dose-rate treatment with either UV or 4NQO when compared to those under high dose-rate treatment. On the other hand, a uvrA- derivative of the repair-proficient which lacks excision rapair ability, showed no reduction in UV- or 4NQO-induced mutation frequencies by lowering the dose-rate. These results support the assumption that excision repair works at higher efficiency for UV- or 4NQO-induced damage in DNA under low dose-rate treatment than under high dose-rate treatment. Mutagenicity of 4NQO was reduced about 20 times in the repair-proficient strain by lowering the dose-rate. The mutation-frequency-versus-dose curve showed, however, no indication of a threshold dose below which bacteria with proficient DNA repair become resistant to mutagenesis.

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