Forespore Engulfment During B subtilis Sporulation

描述（由申请人提供）： 芽孢杆菌属和梭菌属的细菌产生异常持久的内生孢子，这些内生孢子是炭疽和肉毒杆菌中毒的感染因子。吞噬的吞噬样过程是内生孢子形成的标志，因为它在细胞结构内产生独特的细胞，允许孢子组装在细胞质内发生。然而，目前尚不清楚细菌细胞是如何进化出吞噬能力的，因为它们的细胞机制很简单，而且细菌细胞周围的细胞壁似乎是不可逾越的屏障。我们的研究表明，在吞噬过程中的膜迁移是由一个必不可少的蛋白质机器，SpoIID/SpoIIM/SpoIIP复合物，降解细菌细胞壁，加上两个部分冗余的机器，SpoIIQ-SpoIIIAH复合物，提供了一个拉链样的发展细胞和肽聚糖生物合成之间的粘附，这是必不可少的膜迁移时SpoIIQ是缺席。吞噬的最后一步，膜分裂，需要持续的肽聚糖生物合成和SpoIIIE，这也是在孢子形成的不对称定位细胞分裂事件期间染色体分离和隔膜分裂的最后阶段所需的。我们将采取细胞生物学，遗传学和生物化学相结合的方法来研究肽聚糖降解和合成的空间调控，介导吞噬的蛋白质-蛋白质相互作用，并了解细菌细胞催化膜分裂和动态组织的机制。吞噬提供了一种生物学系统来研究对所有细菌都至关重要的细胞生物学事件，例如蛋白质定位和膜融合。 公共卫生相关性： 肽聚糖水解酶存在于所有合成肽聚糖的细菌中，并且是潜在致命的，因为它们的活性必须被严格调节以产生细胞裂解。吞噬提供了一个理想的系统，了解细菌如何控制这些潜在的致命酶，这是有吸引力的目标，为新的抗生素，并有可能确定新的药物靶点的蛋白质，重塑细菌膜或介导的蛋白质定位。

DESCRIPTION (provided by applicant): Bacteria from the genera Bacillus and Clostridium produce unusually durable endospores that are the infectious agent of Anthrax and Botulism. The phagocytosis-like process of engulfment is the hallmark of endospore formation, as it creates the unique cell within a cell structure that allows spore assembly to occur within the cytoplasm. However, it has remained unclear how bacterial cells evolved the ability to perform engulfment given the simplicity of their cellular machinery and the seemingly insurmountable barrier presented by the cell wall that surrounds bacterial cells. Our studies suggest that membrane migration during engulfment is mediated by one essential protein machinery, the SpoIID/SpoIIM/SpoIIP complex that degrades the bacterial cell wall, plus two partially redundant machineries, the SpoIIQ-SpoIIIAH complex that provides a zipper-like adhesion between the developing cells and peptidoglycan biosynthesis which is essential for membrane migration when SpoIIQ is absent. The final step of engulfment, membrane fission, requires both ongoing peptidoglycan biogenesis and SpoIIIE, which is also required for the final stages of chromosome segregation and septal membrane fission during the asymmetrically positioned cell division event of sporulation. We will take a combined cell biological, genetic and biochemical approach to study the spatial regulation of peptidoglycan degradation and synthesis, the protein-protein interactions that mediate engulfment, and to understand the mechanisms by which bacterial cells catalyze membrane fission and are dynamically organized. Engulfment provides a dispensable system to study cell biological events that are essential for all bacteria, such as protein localization and membrane fusion. PUBLIC HEALTH RELEVANCE: Peptidoglycan hydrolases are found in all bacteria that synthesize peptidoglycan, and are potentially lethal because their activity must be strictly regulated to produce cell lysis. Engulfment provides an ideal system for understanding how bacteria control these potentially lethal enzymes, which are attractive targets for novel antibiotics, and has the potential to identify new drug targets in proteins that remodel bacterial membranes or mediate protein localization.