Billen D
J Bacteriol. 1969 Mar;97(3):1169-75. doi: 10.1128/jb.97.3.1169-1175.1969.
New loci of replication along the bacterial chromosome are observed after irradiation of Escherichia coli. It was conjectured that, after X-irradiation, the new initiation site was random with respect to the fixed-origin, whereas, after ultraviolet light exposure, it was selective and appeared to be from the fixed-origin. Evidence presented here shows that, after X-irradiation of E. coli, the new initiation site(s) for the onset of deoxyribonucleic acid replication is induced at chromosomal regions not restricted to the fixed-origin. After ultraviolet light exposure, the new initiation site is preferentially from the fixed-origin. In these studies amino acid starvation was used to synchronize chromosome replication and to allow for differential radioisotopic labeling of the chromosomal origin and terminus. To facilitate interpretation, growing cells actively replicating their chromosome were compared with cells lacking growth points at the time of irradiation. The role of these new replication sites in the observed kinetics of deoxyribonucleic acid replication following X-ray or ultraviolet light exposure is discussed.
对大肠杆菌进行辐照后，可观察到沿细菌染色体出现新的复制位点。据推测，经X射线辐照后，新的起始位点相对于固定原点是随机的，而在紫外线照射后，它是选择性的，且似乎来自固定原点。此处提供的证据表明，对大肠杆菌进行X射线辐照后，脱氧核糖核酸复制起始的新起始位点在不限于固定原点的染色体区域被诱导产生。紫外线照射后，新的起始位点优先来自固定原点。在这些研究中，使用氨基酸饥饿来同步染色体复制，并对染色体的原点和终点进行差异放射性同位素标记。为便于解释，将正在积极复制其染色体的生长细胞与辐照时缺乏生长点的细胞进行了比较。讨论了这些新复制位点在X射线或紫外线照射后所观察到的脱氧核糖核酸复制动力学中的作用。
