Berg D E, Davies J, Allet B, Rochaix J D
Proc Natl Acad Sci U S A. 1975 Sep;72(9):3628-32. doi: 10.1073/pnas.72.9.3628.
Transpositions of segments of R factor (antibiotic resistance plasmids) to bacteriophage lambda have been selected and characterized. Cells of Escherichia coli harboring R factors that determine kanamycin resistance were infected with phage lambda, and lambdakan transducing lines were obtained. Each of the three examined is unusual when compared to lambda transducing phages containing E. coli chromosomal genes: the kan insertions (a) occur at several sites, each well removed from the integration region POP', (b) are not associated with deletion of lambda phage DNA, and (c) are separable from the lambda genome during transduction or during lytic growth. Two insertions from the same R factor contain 1.5 kilobase sequences repeated in inverted order. The properties of the lambdakan phage suggest that R factors contain systems capable of mediating genetic exchange in the absence of extensive DNA homology. It is suggested that such systems of exchange may have played important roles in R factor evolution.
已筛选并鉴定了R因子（抗生素抗性质粒）片段向噬菌体λ的转位。用噬菌体λ感染携带决定卡那霉素抗性的R因子的大肠杆菌细胞，获得了λKan转导系。与含有大肠杆菌染色体基因的λ转导噬菌体相比，所检测的三种转导系中的每一种都不寻常：卡那霉素插入片段（a）出现在几个位点，每个位点都远离整合区域POP'；（b）与λ噬菌体DNA的缺失无关；（c）在转导或裂解生长过程中可与λ基因组分离。来自同一R因子的两个插入片段包含以相反顺序重复的1.5千碱基序列。λKan噬菌体的特性表明，R因子含有能够在缺乏广泛DNA同源性的情况下介导基因交换的系统。有人提出，这种交换系统可能在R因子的进化中发挥了重要作用。
