Marczynski G T, Dingwall A, Shapiro L
Department of Developmental Biology, Stanford University School of Medicine, CA 94305.
J Mol Biol. 1990 Apr 20;212(4):709-22. doi: 10.1016/0022-2836(90)90232-B.
Cell division in Caulobacter crescentus yields a swarmer and a stalked cell. Only the stalked cell progeny is able to replicate its chromosome, and the swarmer cell progeny must differentiate into a stalked cell before it too can replicate its chromosome. In an effort to understand the mechanisms that limit chromosomal replication to the stalked cell, plasmid DNA synthesis was analyzed during the developmental cell cycle of C. crescentus, and the partitioning of both the plasmids and the chromosomes to the progeny cells was examined. Unlike the chromosome, plasmids from the incompatibility groups Q and P replicated in all C. crescentus cell types. However, all plasmids tested showed a ten- to 20-fold higher replication rate in the stalked cells than the swarmer cells. We observed that all plasmids replicated during the C. crescentus cell cycle with comparable kinetics of DNA synthesis, even though we tested plasmids that encode very different known (and putative) replication proteins. We determined the plasmid copy number in both progeny cell types, and determined that plasmids partitioned equally to the stalked and swarmer cells. We also reexamined chromosome partitioning in a recombination-deficient strain of C. crescentus, and confirmed an earlier report that chromosomes partition to the progeny stalked and swarmer cells in a random manner that does not discriminate between old and new DNA strands.
新月柄杆菌的细胞分裂产生一个游动细胞和一个柄细胞。只有柄细胞后代能够复制其染色体，游动细胞后代必须先分化为柄细胞，才能复制其染色体。为了了解将染色体复制限制在柄细胞中的机制，在新月柄杆菌的发育细胞周期中分析了质粒DNA的合成，并研究了质粒和染色体向子代细胞的分配。与染色体不同，来自不相容群Q和P的质粒在所有新月柄杆菌细胞类型中都能复制。然而，所有测试的质粒在柄细胞中的复制速率比游动细胞高10到20倍。我们观察到，所有质粒在新月柄杆菌细胞周期中复制时，DNA合成动力学相似，尽管我们测试的质粒编码非常不同的已知（和推定的）复制蛋白。我们确定了两种子代细胞类型中的质粒拷贝数，并确定质粒在柄细胞和游动细胞中平均分配。我们还重新检查了新月柄杆菌重组缺陷菌株中的染色体分配，并证实了之前的一份报告，即染色体以随机方式分配到子代柄细胞和游动细胞中，不区分新旧DNA链。
