Koppes L J
Department of Microbiology, University of Uppsala, Sweden.
Mol Gen Genet. 1987 Aug;209(1):188-92. doi: 10.1007/BF00329857.
The variability of the time interval between successive rounds of chromosome replication was estimated by density-shift experiments, by measuring the conversion of heavy DNA to hybrid density and light DNAs upon transfer of a steady-state culture growing in medium with [13C]glucose and 15NH4Cl to medium with light isotopes. The coefficient of variation (CV%) for the interreplication time of the Escherichia coli K12 chromosome was found to be 17%, i.e. similar to that for interdivision time. The presence of additional copies of oriC in the cell on a high copy number plasmid did not increase the CV of interreplication time. It is concluded that a single rate-limiting event is unlikely to time the initiation of chromosome replication. The regulation of initiation at oriC and the coordination with cell division is discussed.
通过密度转移实验估计连续两轮染色体复制之间的时间间隔变异性，即通过测量在含有[13C]葡萄糖和15NH4Cl的培养基中生长的稳态培养物转移到含有轻同位素的培养基时，重DNA向杂种密度和轻DNA的转化情况。发现大肠杆菌K12染色体复制间隔时间的变异系数（CV%）为17%，即与细胞分裂间隔时间的变异系数相似。细胞中高拷贝数质粒上oriC的额外拷贝的存在并未增加复制间隔时间的CV。得出结论，单个限速事件不太可能为染色体复制的起始定时。文中讨论了oriC处起始的调控以及与细胞分裂的协调。
