Spatiotemporal regulation of bacterial cell envelope assembly

项目摘要/摘要 尽管细菌细胞体积很小，但它们在空间和时间上精确地同步了细胞的过程。单元格 细菌的包膜是在细胞周期中协调组装的复杂而动态的结构。 革兰氏阳性菌的细胞壁锚定表面蛋白是主要的细胞膜成分，它们是 通过细胞质膜分泌，并通过索尔特酶A共价连接到细胞壁肽聚糖 (SrtA)值得注意的是，许多表面蛋白都含有一种特异的YSIRK/G-S信号肽，该信号肽可以靶向 细胞分裂时的交叉壁。与细胞分裂和细胞壁合成相协调，跨壁靶向 促进表面蛋白有效地结合到新合成的跨壁肽聚糖；然而， 其机制仍不清楚。已有研究提出YSIRK/G-S信号肽促进局部化 分隔处的分泌物。然而，通过在我们的模型生物体中开发一种新的显微镜方法 金黄色葡萄球菌，我们现在提供的证据表明，与流行的模型相反，靶向不 发生在分泌过程中，而不是依赖于srtA。我们进一步发现，跨墙靶向是受调控的 通过另一个重要的细胞膜成分：LTAS介导的脂磷壁酸(LTA)合成和D- 磷壁酸的丙二酰化。有趣的是，LTA合成和D-丙氨酸化调节不同的生物发生阶段： LTA调节srtA介导的间隔锚定，而D-丙氨酸氨基转移调节跨壁沉积。 总的来说，这些来自我自己实验室的最新发现构成了我独立研究计划的基础 这个Mira应用程序。我们将阐明YSIRK/G-S信号肽Lta的不同机制 在细胞周期中，合成和D-丙氨酸化在空间上调节表面蛋白的生物发生。成功 研究项目的完成不仅将揭示表面蛋白生物发生的新机制 在革兰氏阳性细菌中，还发现了LTA和D-丙氨酸化在细胞被膜组装中的新功能， 提供了对细菌细胞如何在生长过程中精确协调细胞膜组装的基本见解 和细胞分裂。

Project Summary/Abstract Despite their small size, bacterial cells precisely synchronize cellular processes in space and time. The cell envelopes of bacteria are complex and dynamic structures that are coordinately assembled during the cell cycle. Cell wall anchored surface proteins of Gram-positive bacteria are major cell envelope components, which are secreted across the cytoplasmic membrane and covalently attached to cell wall peptidoglycan by sortase A (SrtA). Strikingly, many surface proteins contain a specific YSIRK/G-S signal peptide that targets proteins to the cross-wall during cell division. Coordinated with cell division and cell wall synthesis, cross-wall targeting promotes efficient incorporation of surface proteins to the newly synthesized cross-wall peptidoglycan; however, the mechanisms remain unknown. It has been proposed that the YSIRK/G-S signal peptide promotes localized secretion at the division septum. However, by developing a new microscopy method in our model organism of Staphylococcus aureus, we now provide evidence that in contrast to the prevailing model, the targeting does not occur during secretion, but rather is SrtA-dependent. We further discovered that cross-wall targeting is regulated by another important cell envelope component: LtaS-mediated lipoteichoic acid (LTA) synthesis and D- alanylation of teichoic acids. Intriguingly, LTA synthesis and D-alanylation regulate different biogenesis stages: LTA regulates SrtA-mediated septal anchoring whereas D-alanylation modulates cross-wall deposition. Collectively, these recent discoveries from my own lab form the foundation of my independent research program for this MIRA application. We will elucidate the distinct mechanisms by which the YSIRK/G-S signal peptide, LTA synthesis and D-alanylation spatially regulate surface protein biogenesis during the cell cycle. Successful completion of the research projects will not only reveal novel mechanisms underlying surface protein biogenesis in Gram-positive bacteria, but also uncover novel functions of LTA and D-alanylation in cell envelope assembly, providing fundamental insight into how bacterial cells precisely coordinate cell envelope assembly during growth and cell division.