Sun Q, Yu X C, Margolin W
Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030, USA.
Mol Microbiol. 1998 Jul;29(2):491-503. doi: 10.1046/j.1365-2958.1998.00942.x.
The FtsZ ring assembles between segregated daughter chromosomes in prokaryotic cells and is essential for cell division. To understand better how the FtsZ ring is influenced by chromosome positioning and structure in Escherichia coli, we investigated its localization in parC and mukB mutants that are defective for chromosome segregation. Cells of both mutants at non-permissive temperatures were either filamentous with unsegregated nucleoids or short and anucleate. In parC filaments, FtsZ rings tended to localize only to either side of the central unsegregated nucleoid and rarely to the cell midpoint; however, medial rings reappeared soon after switching back to the permissive temperature. Filamentous mukB cells were usually longer and lacked many potential rings. At temperatures permissive for mukB viability, medial FtsZ rings assembled despite the presence of apparently unsegregated nucleoids. However, a significant proportion of these FtsZ rings were mislocalized or structurally abnormal. The most surprising result of this study was revealed upon further examination of FtsZ ring positioning in anucleate cells generated by the parC and mukB mutants: many of these cells, despite having no chromosome, possessed FtsZ rings at their midpoints. This discovery strongly suggests that the chromosome itself is not required for the proper positioning and development of the medial division site.
FtsZ环在原核细胞中分隔的子代染色体之间组装，对细胞分裂至关重要。为了更好地理解FtsZ环如何受大肠杆菌中染色体定位和结构的影响，我们研究了其在染色体分离存在缺陷的parC和mukB突变体中的定位。在非允许温度下，这两种突变体的细胞要么呈丝状且核质未分离，要么短小且无核。在parC丝状细胞中，FtsZ环往往仅定位于中央未分离核质的两侧，很少定位于细胞中点；然而，在恢复到允许温度后不久，中间环又重新出现。丝状mukB细胞通常更长，且缺少许多潜在的环。在允许mukB存活的温度下，尽管存在明显未分离的核质，中间的FtsZ环仍会组装。然而，这些FtsZ环中有很大一部分定位错误或结构异常。在进一步检查由parC和mukB突变体产生的无核细胞中的FtsZ环定位时，揭示了这项研究最令人惊讶的结果：这些细胞中有许多尽管没有染色体，但在其中点处仍有FtsZ环。这一发现强烈表明，中间分裂位点的正确定位和形成并不需要染色体本身。
