Kinetics of plasmid segregation in Escherichia coli
Kinetics of plasmid segregation in Escherichia coli
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DOI：
10.1046/j.1365-2958.2003.03837.x
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发表时间：
2004-01-01
影响因子：
3.6
通讯作者：
Wright, A
中科院分区：
文献类型：
--
作者：
Gordon, S;Rech, J;Wright, A
低拷贝数的细菌复制子在其宿主细胞中占据特定位置。生产的GFP-Lac阻遏物杂合蛋白的细胞携带F或P1质粒标记的乳糖操纵子阵列显示，在较小的（年轻）细胞中，这些质粒被视为主要是作为一个单一的荧光焦点在中间细胞，而较大的细胞往往有两个焦点，一个在每个四分之一的细胞位置。中心焦点的复制被认为代表质粒拷贝的主动分配。我们在这里报告我们的调查，通过延时显微镜的后续运动，这些副本的四分之一的位置。在中央焦点复制之后，新的焦点迅速地直接迁移到它们的四分之一细胞目的地，在那里它们一直保持到下一个细胞周期。其移动速度比oriC向极迁移快约5倍，比细胞伸长快50倍。mini-F缺乏其sopC着丝粒的异常定位证明了在此定位过程中对分区系统的要求。从每个细胞的F质粒拷贝数的测量值来看，似乎每个迁移焦点含有两个或更多个质粒分子。这种聚类的分子基础，并在细胞周期中的分区事件的分阶段的证据，进行了讨论。
Low copy-number bacterial replicons occupy specific locations in their host cells. Production of a GFP-Lac repressor hybrid protein in cells carrying F or P1 plasmids tagged with a lac operator array reveals that in smaller (younger) cells these plasmids are seen mainly as a single fluorescent focus at mid-cell, whereas larger cells tend to have two foci, one at each quarter-cell position. Duplication of the central focus is presumed to represent active partition of plasmid copies. We report here our investigation by time-lapse microscopy of the subsequent movement of these copies to the quarter positions. Following duplication of the central focus, the new foci migrated rapidly and directly to their quarter-cell destinations, where they remained until the next cell cycle. The speed of movement was about five times faster than poleward migration of oriC and 50 times faster than cell elongation. Aberrant positioning of mini-F lacking its sopC centromere demonstrated the requirement for the partition system in this localization process. From the measured number of F plasmid copies per cell it appears that each migrating focus contains two or more plasmid molecules. The molecular basis of this clustering, and evidence for phasing of the partition event in the cell cycle, are discussed.