Yoshikawa M
J Bacteriol. 1974 Jun;118(3):1123-31. doi: 10.1128/jb.118.3.1123-1131.1974.
A stable Hfr strain of Escherichia coli K-12 was obtained by integrative suppression by an R factor, R100-1. The R factor was integrated into the right of 81 min, and chromosome transfer occurred counterclockwise. Mating experiments revealed two linkage groups of genes on the R factor. Drug-resistant transductants of a dnaA-ts recipient from an R-factor Hfr and from an R(+) strain differ in their drug resistance patterns, temperature sensitivity, and transferability of drug resistance as well as chromosome markers. Transductants that transferred chromosome markers were further classified as to the origin and direction of chromosome transfer. For temperature-sensitive transductants, the reversion frequency to temperature resistance was determined, and these revertants were scored for transfer of drug resistance as well as chromosome markers. Two genes responsible for integrative suppression (designated as repA) and the other for autonomous replication (designated as repB) were identified and mapped. The arrangement of genes on the R factor is... (sul, str, cml)... repA... tra... (tet, repB).... The map of the autonomously replicating R factor is probably a circle connecting both sides of this linear map. Thus, a method has been established to map a plasmid that could not finely be analyzed under autonomous state by transduction. It also permits genetic analysis of genes responsible for replication of the plasmid without making use of a conditional mutant of itself but with that of the host, dnaA.
通过R因子R100 - 1的整合抑制获得了大肠杆菌K - 12的稳定高频重组(Hfr)菌株。R因子整合到81分钟处的右侧,染色体转移呈逆时针方向。交配实验揭示了R因子上的两个基因连锁群。来自R因子Hfr和R(+)菌株的dnaA - ts受体的耐药转导子在耐药模式、温度敏感性、耐药性以及染色体标记的转移性方面存在差异。转移染色体标记的转导子进一步根据染色体转移的起源和方向进行分类。对于温度敏感转导子,测定了其对温度抗性的回复频率,并对这些回复子的耐药性以及染色体标记的转移进行了评分。鉴定并定位了两个负责整合抑制的基因(命名为repA)和另一个负责自主复制的基因(命名为repB)。R因子上基因的排列是……(sul,str,cml)……repA……tra……(tet,repB)……。自主复制的R因子的图谱可能是一个连接该线性图谱两侧的环。因此,建立了一种对在自主状态下无法通过转导进行精细分析的质粒进行定位的方法。它还允许在不使用质粒自身的条件突变体而是利用宿主dnaA的条件突变体的情况下,对负责质粒复制的基因进行遗传分析。