Clewell D B
J Bacteriol. 1972 May;110(2):667-76. doi: 10.1128/jb.110.2.667-676.1972.
The colicinogenic factor E(1) (Col E(1)) in Escherichia coli continues to replicate by a semiconservative mechanism in the presence of chloramphenicol (CAP) for 10 to 15 hr, long after chromosomal deoxyribonucleic acid (DNA) synthesis has terminated. Following CAP addition, the rate of synthesis of plasmid DNA gradually increases to an extent dependent on the medium employed. Within 2 to 4 hr after the addition of CAP, replication in a glucose-Casamino Acids medium approaches a maximum rate representing approximately eight times an average rate which would be required for a net doubling of DNA per cell in one generation. The number of copies of Col E(1) DNA molecules that accumulate under these conditions approaches about 3,000 copies per cell, representing a 125-fold increase over the normal level of 24 copies per cell. The system is particularly convenient for studying the mechanism of DNA replication.
大肠杆菌中的产大肠杆菌素因子E(1)（Col E(1)）在氯霉素（CAP）存在的情况下，会通过半保留机制持续复制10至15小时，这是在染色体脱氧核糖核酸（DNA）合成终止很长时间之后。添加CAP后，质粒DNA的合成速率会逐渐增加，增加的程度取决于所用的培养基。添加CAP后2至4小时内，在葡萄糖-酪蛋白氨基酸培养基中的复制接近最大速率，该最大速率约为每个细胞中DNA净加倍所需平均速率的八倍。在这些条件下积累的Col E(1) DNA分子拷贝数接近每个细胞约3000个拷贝，比每个细胞正常的24个拷贝水平增加了125倍。该系统对于研究DNA复制机制特别方便。
