Department of Molecular Biology, Massachusetts General Hospital, Boston, MA, USA.
Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA, USA.
Nat Microbiol. 2022 Oct;7(10):1621-1634. doi: 10.1038/s41564-022-01210-z. Epub 2022 Sep 12.
The bacterial division apparatus catalyses the synthesis and remodelling of septal peptidoglycan (sPG) to build the cell wall layer that fortifies the daughter cell poles. Understanding of this essential process has been limited by the lack of native three-dimensional views of developing septa. Here, we apply state-of-the-art cryogenic electron tomography (cryo-ET) and fluorescence microscopy to visualize the division site architecture and sPG biogenesis dynamics of the Gram-negative bacterium Escherichia coli. We identify a wedge-like sPG structure that fortifies the ingrowing septum. Experiments with strains defective in sPG biogenesis revealed that the septal architecture and mode of division can be modified to more closely resemble that of other Gram-negative (Caulobacter crescentus) or Gram-positive (Staphylococcus aureus) bacteria, suggesting that a conserved mechanism underlies the formation of different septal morphologies. Finally, analysis of mutants impaired in amidase activation (ΔenvC ΔnlpD) showed that cell wall remodelling affects the placement and stability of the cytokinetic ring. Taken together, our results support a model in which competition between the cell elongation and division machineries determines the shape of cell constrictions and the poles they form. They also highlight how the activity of the division system can be modulated to help generate the diverse array of shapes observed in the bacterial domain.
细菌分裂装置催化隔膜肽聚糖 (sPG) 的合成和重塑，以构建加固子细胞两极的细胞壁层。由于缺乏发育中隔膜的天然三维视图，对这一基本过程的理解受到限制。在这里，我们应用最先进的低温电子断层扫描 (cryo-ET) 和荧光显微镜技术，可视化革兰氏阴性细菌大肠杆菌的分裂部位结构和 sPG 生物发生动力学。我们确定了一个楔形的 sPG 结构，加固了正在生长的隔膜。用 sPG 生物发生缺陷的菌株进行的实验表明，隔膜结构和分裂方式可以被修改，使其更类似于其他革兰氏阴性（新月柄杆菌）或革兰氏阳性（金黄色葡萄球菌）细菌，这表明不同隔膜形态的形成有一个保守的机制。最后，对缺乏酰胺酶激活的突变体（ΔenvC ΔnlpD）的分析表明，细胞壁重塑会影响细胞分裂环的位置和稳定性。总之，我们的结果支持了这样一种模型，即细胞伸长和分裂机制之间的竞争决定了细胞缢缩的形状以及它们形成的两极。它们还突出了如何调节分裂系统的活性来帮助产生在细菌领域观察到的各种形状。
