Mudgett J S, Manzella J M, Taylor W D
Department of Molecular and Cell Biology, Pennsylvania State University, University Park 16802.
Radiat Res. 1990 Oct;124(1):57-61.
Plasmid DNA was used to study gamma-radiation-induced recombination and mutagenesis in Escherichia coli host cells. Plasmid pBRP1, a derivative of pBR322 containing the lac operon of E. coli, was irradiated with 60Co gamma rays prior to transformation into E. coli strains of different recA and lac genotypes. Plasmid-chromosome recombination was assayed in lacY1 host cells, whereas plasmid mutagenesis was assayed in delta lac host cells lacking chromosomal sequences homologous to the plasmid. Both recombinant and mutant plasmids were identified by the phenotypic changes in lactose utilization, and confirmed by restriction analysis of isolated plasmids. Plasmid-chromosome recombination was induced to high levels (about 20% of survivors at 700 Gy) and was dependent on the host recA gene. Plasmid mutagenesis occurred at lower levels (about 1.5% of survivors at 600 Gy) and was relatively independent of the recA gene. Plasmid survival was unaffected by the presence or absence of host recA mutations or the potential for plasmid-chromosome recombination.
质粒DNA被用于研究γ射线诱导的大肠杆菌宿主细胞中的重组和诱变作用。质粒pBRP1是pBR322的衍生物，含有大肠杆菌的乳糖操纵子，在转化到不同recA和lac基因型的大肠杆菌菌株之前，用60Co γ射线进行辐照。在lacY1宿主细胞中检测质粒-染色体重组，而在缺乏与质粒同源染色体序列的δ lac宿主细胞中检测质粒诱变。通过乳糖利用的表型变化鉴定重组质粒和突变质粒，并通过对分离质粒的限制性分析进行确认。质粒-染色体重组被诱导到高水平（在700 Gy时约20%的存活者），并且依赖于宿主recA基因。质粒诱变发生水平较低（在600 Gy时约1.5%的存活者），并且相对独立于recA基因。宿主recA突变的存在与否或质粒-染色体重组的可能性对质粒存活没有影响。
