Donachie W D, Addinall S, Begg K
Institute of Cell and Molecular Biology, University of Edinburgh, Scotland.
Bioessays. 1995 Jun;17(6):569-76. doi: 10.1002/bies.950170616.
In the rod-shaped cells of E. coli, chromosome segregation takes place immediately after replication has been completed. A septum then forms between the two sister chromosomes. In the absence of certain membrane proteins, cells grow instead as large, multichromosomal spheres that divide successively in planes that are at right angles to one another. Although multichromosomal, the spherical cells cannot be maintained as heterozygotes. These observations imply that, in these mutants, each individual chromosome gives rise to a separate clone of descendant cells. This suggests a model in which sites for cell division form between pairs of sister chromosomes at the time of segregation, but are not used in spherical cells until further rounds of replication have taken place, thus ensuring clonal ('hierarchical') segregation of chromosomes into progeny cells. The role of the morphogenetic membrane proteins is to convert the basically spherical cell into a cylinder that is able to divide as soon as replication and segregation have been completed, and thus to maximise the number of viable cells per genome.
在大肠杆菌的杆状细胞中，染色体分离在复制完成后立即发生。然后在两条姐妹染色体之间形成隔膜。在缺乏某些膜蛋白的情况下，细胞会 instead 生长成大型的多染色体球体，这些球体在相互垂直的平面上相继分裂。尽管是多染色体的，但球形细胞不能作为杂合子维持。这些观察结果表明，在这些突变体中，每个单独的染色体都会产生一个单独的后代细胞克隆。这提示了一种模型，即细胞分裂位点在分离时在姐妹染色体对之间形成，但在球形细胞中直到进行进一步的复制轮次才会被使用，从而确保染色体向子代细胞的克隆性（“分层”）分离。形态发生膜蛋白的作用是将基本呈球形的细胞转化为一个圆柱体，一旦复制和分离完成就能进行分裂，从而使每个基因组产生的活细胞数量最大化。
