Forespore Engulfment During B subtilis Sporulation

描述(申请人提供)：芽孢杆菌属和梭状芽胞杆菌属的细菌产生异常持久和长寿的孢子，这些孢子是炭疽和肉毒杆菌中毒的感染源，并聚集在另一个细胞的细胞质中。细胞结构(内孢子)中的这种独特的细胞是由一种被称为吞噬的吞噬过程产生的。在吞噬过程中，较大的母细胞的膜在较小的前孔周围迁移，直到它完全被包围在母细胞的细胞质中。吞噬作用为细菌细胞的动态能力提供了一个戏剧性的例子，但其机制尚不清楚。我们已经开发了新的工具来研究吞噬、膜融合和蛋白质定位，并发现了在这些步骤中存在缺陷的突变体。融合缺陷突变体在吞噬和细胞分裂的最后一步都是缺陷的，并影响到一种保守的蛋白质，该蛋白质也参与了染色体分离的最后阶段。我们建议这些蛋白质协调染色体分离与细胞分裂的完成，以确保细胞分离不会损害不完全分离的染色体。我们还确定了膜在前孔周围移动的两种机制，其中一种依赖于SpollD肽聚糖水解酶。我们将采用细胞生物学、遗传学和生物化学相结合的方法来研究肽聚糖水解的空间调节，以及介导吞噬的蛋白质-蛋白质相互作用，以及了解细菌细胞催化膜融合和动态组织的机制。吞噬作用为研究所有细菌所必需的细胞生物学事件提供了一个不可或缺的系统，如蛋白质定位和膜融合。它还需要肽聚糖水解酶，这种酶存在于所有合成肽聚糖的细菌中，并且是潜在的致命的，因为它们的活性可以导致细胞溶解，而不是严格的空间和时间调节。事实上，许多商业抗生素的杀伤力需要这些水解酶。吞噬为了解细菌如何控制这些潜在的致命酶提供了一个理想的系统，这些酶是新抗生素的诱人靶标，并有可能在蛋白质中识别新的药物靶点，这些蛋白质可以重塑细菌膜或介导细菌蛋白质的定位。

DESCRIPTION (provided by applicant): Bacteria from the genera Bacillus and Clostridium produce unusually durable and long lived spores that are the infectious agent of Anthrax and Botulism, and which are assembled in the cytoplasm of another cell. This unique cell within a cell structure (the endospore) is produced by a phagocytosis-like process known as engulfment. During engulfment, the membrane of the larger mother cell migrates around the smaller forespore, until it is completely enclosed within the mother cell cytoplasm. Engulfment provides a dramatic example of the dynamic capabilities of the bacterial cell, but its mechanism remains unclear. We have developed new tools for the study of engulfment, membrane fusion and protein localization and identified mutants defective in these steps. The fusion defective mutant is defective in both the final step of engulfment and cell division, and affects a conserved protein also involved in the final stages of chromosome segregation. We suggest that these proteins coordinate chromosome segregation with the completion of cell division, to ensure that cell separation does not damage an incompletely segregated chromosome. We have also identified two mechanisms by which the membranes move around the forespore, one of which depends on the SpollD peptidoglycan hydrolase. We will take a combined cell biological, genetic and biochemical approach to study the spatial regulation of peptidoglycan hydrolysis, the protein-protein interactions that mediate engulfment, as well as to understand the mechanisms by which bacterial cells catalyze membrane fusion 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. It also requires peptidoglycan hydrolases, which are found in all bacteria that synthesize peptidoglycan, and which are potentially lethal because their activity can result in cell lysis without strict spatial and temporal regulation. Indeed, the lethality of many commercial antibiotics requires these hydrolytic enzymes. 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 localization of bacterial proteins.