Bacterial cell wall synthesis, shape and septation

描述(申请人提供)：细菌细胞壁在几个关键的生物学过程中起着基本的作用，包括保护微生物免受渗透压力的溶解，并有助于亚细胞组织和整体形态。肽聚糖的片段是壁层的结构骨架，对人类和动物起到毒素的作用，并成为这些高等生物体天然免疫反应的靶标。此外，通过赋予细菌不同的形状，壁会产生极性，影响细菌的分化，并直接或间接地促进营养积累、附着在表面、运动性、染色体分离、避免捕食者、生物膜的形成和致病。因此，这个领域解决了既基本又实用的问题：基本的，考虑细胞是如何构建的；以及实用的，因为这些特性有助于细菌的毒力并决定抗生素治疗的有效性。这个项目的长期目标是了解肽聚糖的结构、合成、调节和功能含义，以及产生和修饰它的酶。更具体地说，我们希望知道细胞如何将其壁区分为结构和功能域，它们如何在细胞分裂过程中处理壁，以及它们如何塑造它以产生不同形状的细胞。最近的发现表明，最重要的细胞分裂蛋白FtsZ在启动和指导细胞分裂方面发挥的作用远远超过其公认的作用。首先，分裂依赖于肽聚糖修饰酶的活性，当这种关系受到干扰时，可能会导致细胞溶解。其次，现在很明显，FtsZ指导着整个细胞周期的细胞壁合成：随着细菌的伸长，扩散到侧壁；在细胞分裂开始之前，在细胞中心的一个集中的窄带中；以及在细胞分裂的收缩阶段。我们建议通过追求以下特定目标来扩展和完善我们对细菌生理学这些方面的理解：1)更密切地研究驱动FtsZ依赖的肽聚糖合成的机制，2)表征与FtsZ相关的新表型，以及3)确定细胞壁的结构。这些目标将通过定义与FtsZ一起负责不同类型的肽聚糖合成的蛋白质，通过分离和表征与FtsZ和细胞壁合成相交的途径中的突变，以及通过创造新的工具来检查细胞壁的化学性质来实现。了解细胞完整性、细胞形状和分裂的过程将有助于了解肽聚糖合成的起源、结构和拓扑调节，以及一般的原核形态。与公共健康相关：坚硬的细胞壁对细菌的生存至关重要，而我们最重要的大量抗生素会抑制产生这种保护结构的蛋白质。由于抗生素耐药性正在增加，完全了解细菌壁是如何形成的，构成细菌壁的蛋白质的活性，以及它的最终结构是什么，变得尤为迫切。这个项目将通过发现蛋白质相互作用来合成细胞壁的方式，并通过创造可视化其分子组成的新工具来实现这一目标。

DESCRIPTION (provided by applicant): The bacterial cell wall plays a fundamental role in several critical biological processes, including protecting microorganisms against lysis by osmotic pressure and contributing to subcellular organization and overall morphology. Fragments of peptidoglycan, the structural backbone of the wall, function as toxins toward humans and animals and are targeted by the innate immune response in these higher organisms. In addition, by imparting to bacteria their different shapes, the wall creates polarities, influences bacterial differentiation, and contributes directly or indirectly to nutrient accumulation, attachment to surfaces, motility, chromosomal segregation, predator avoidance, biofilm formation, and pathogenesis. Thus, this field addresses concerns that are both basic and practical: basic, in considering how cells are constructed; and practical, because these characteristics contribute to bacterial virulence and determine the effectiveness of antibiotic therapy. The long-term goal of this project is to understand the structure, synthesis, regulation and functional implications of peptidoglycan and the enzymes that create and modify it. More specifically, we wish to know how cells differentiate their walls into structural and functional domains, how they process the wall during cell division, and how they mold it to produce cells of different shapes. Recent discoveries demonstrate that the premier cell division protein, FtsZ, does far more than its acknowledged role in initiating and directing cell division. First, division relies on the activities of peptidoglycan-modifying enzymes, and this relationship, when disturbed, can lead to cell dissolution. Second, it is now apparent that FtsZ directs cell wall synthesis throughout the cell cycle: diffusely into the sidewalls as bacteria elongate; in a concentrated narrow band at the cell center prior to the initiation of septation; and during the constriction phase of cell division. We propose to extend and refine our understanding of these aspects of bacterial physiology by pursuing the following specific aims: 1) examining more closely the mechanisms that drive FtsZ-dependent peptidoglycan synthesis, 2) characterizing new phenotypes associated with FtsZ, and 3) determining the structure of the cell wall. These goals will be realized by defining the proteins that, along with FtsZ, are responsible for the different types of peptidoglycan synthesis, by isolating and characterizing mutations in pathways that intersect with FtsZ and cell wall synthesis, and by creating new tools to examine the chemical nature of the wall. Understanding the processes underlying cellular integrity, cell shape and division will shed light on the genesis, structure and topological regulation of peptidoglycan synthesis and on prokaryotic morphology in general. PUBLIC HEALTH RELEVANCE: A rigid cell wall is essential for bacterial survival, and a large number of our most important antibiotics inhibit the proteins that create this protective structure. Because antibiotic resistance is increasing, it has become especially urgent to understand completely how the bacterial wall is made, the activities of the proteins that make it, and what its final structure looks like. This project will approach this goal by discovering ways in which proteins interact to synthesize the cell wall and by creating new tools for visualizing its molecular composition.