Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 2012 Mar 6;109(10):E595-604. doi: 10.1073/pnas.1117132109. Epub 2012 Feb 17.
The regulation of cell shape is a common challenge faced by organisms across all biological kingdoms. In nearly all bacteria, cell shape is determined by the architecture of the peptidoglycan cell wall, a macromolecule consisting of glycan strands crosslinked by peptides. In addition to shape, cell growth must also maintain the wall structural integrity to prevent lysis due to large turgor pressures. Robustness can be accomplished by establishing a globally ordered cell-wall network, although how a bacterium generates and maintains peptidoglycan order on the micron scale using nanometer-sized proteins remains a mystery. Here, we demonstrate that left-handed chirality of the MreB cytoskeleton in the rod-shaped bacterium Escherichia coli gives rise to a global, right-handed chiral ordering of the cell wall. Local, MreB-guided insertion of material into the peptidoglycan network naturally orders the glycan strands and causes cells to twist left-handedly during elongational growth. Through comparison with the right-handed twisting of Bacillus subtilis cells, our work supports a common mechanism linking helical insertion and chiral cell-wall ordering in rod-shaped bacteria. These physical principles of cell growth link the molecular structure of the bacterial cytoskeleton, mechanisms of wall synthesis, and the coordination of cell-wall architecture.
细胞形状的调控是所有生物界面临的共同挑战。在几乎所有细菌中，细胞形状由肽聚糖细胞壁的结构决定，肽聚糖是由糖链通过肽交联而成的大分子。除了形状，细胞生长还必须保持细胞壁结构的完整性，以防止由于高渗透压而裂解。通过建立一个全局有序的细胞壁网络可以实现稳健性，尽管细菌如何使用纳米级大小的蛋白质在微米尺度上产生和维持肽聚糖的有序性仍然是一个谜。在这里，我们证明了杆状细菌大肠杆菌中 MreB 细胞骨架的左手手性导致细胞壁的全局、右手手性有序。局部的、MreB 指导的物质插入到肽聚糖网络中自然地排列糖链，并在伸长生长过程中导致细胞向左扭转。通过与枯草芽孢杆菌细胞的右旋扭曲进行比较，我们的工作支持了一种将螺旋插入和细胞壁手性有序化联系起来的共同机制，这种链接在杆状细菌中。这些细胞生长的物理原理将细菌细胞骨架的分子结构、细胞壁合成的机制以及细胞壁结构的协调联系起来。
