Bailey Matthew W, Bisicchia Paola, Warren Boyd T, Sherratt David J, Männik Jaan
Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee, United States of America.
Department of Biochemistry, University of Oxford, Oxford, United Kingdom.
PLoS Genet. 2014 Aug 7;10(8):e1004504. doi: 10.1371/journal.pgen.1004504. eCollection 2014 Aug.
Cell division in Escherichia coli starts with assembly of FtsZ protofilaments into a ring-like structure, the Z-ring. Positioning of the Z-ring at midcell is thought to be coordinated by two regulatory systems, nucleoid occlusion and the Min system. In E. coli, nucleoid occlusion is mediated by the SlmA proteins. Here, we address the question of whether there are additional positioning systems that are capable of localizing the E. coli divisome with respect to the cell center. Using quantitative fluorescence imaging we show that slow growing cells lacking functional Min and SlmA nucleoid occlusion systems continue to divide preferentially at midcell. We find that the initial Z-ring assembly occurs over the center of the nucleoid instead of nucleoid-free regions under these conditions. We determine that Z-ring formation begins shortly after the arrival of the Ter macrodomain at the nucleoid center. Removal of either the MatP, ZapB, or ZapA proteins significantly affects the accuracy and precision of Z-ring positioning relative to the nucleoid center in these cells in accordance with the idea that these proteins link the Ter macrodomain and the Z-ring. Interestingly, even in the absence of Min, SlmA, and the putative Ter macrodomain - Z-ring link, there remains a weak midcell positioning bias for the Z-ring. Our work demonstrates that additional Z-ring localization systems are present in E. coli than are known currently. In particular, we identify that the Ter macrodomain acts as a landmark for the Z-ring in the presence of MatP, ZapB and ZapA proteins.
大肠杆菌中的细胞分裂始于FtsZ原丝组装成环状结构，即Z环。Z环在细胞中部的定位被认为是由两个调节系统协调的，即类核阻隔和Min系统。在大肠杆菌中，类核阻隔由SlmA蛋白介导。在这里，我们探讨是否存在其他定位系统，能够使大肠杆菌的分裂体相对于细胞中心进行定位。通过定量荧光成像，我们发现缺乏功能性Min和SlmA类核阻隔系统的缓慢生长细胞继续优先在细胞中部进行分裂。我们发现在这些条件下，最初的Z环组装发生在类核中心上方，而不是无类核区域。我们确定Z环形成在Ter大结构域到达类核中心后不久开始。去除MatP、ZapB或ZapA蛋白会显著影响这些细胞中Z环相对于类核中心定位的准确性和精确性，这与这些蛋白连接Ter大结构域和Z环的观点一致。有趣的是，即使在没有Min、SlmA以及假定的Ter大结构域-Z环连接的情况下，Z环仍存在微弱的细胞中部定位偏差。我们的工作表明，大肠杆菌中存在比目前已知的更多的Z环定位系统。特别是，我们确定在存在MatP、ZapB和ZapA蛋白的情况下，Ter大结构域作为Z环的一个标志。
