Elucidation of a bacterial cell shape generating program and pathogenic functions

描述(申请人提供)：幽门螺杆菌是一种螺旋杆状细菌，定植于人的胃中，导致从轻度胃炎到消化性溃疡和胃癌的一系列临床结果。大多数对幽门螺杆菌毒力的描述包括被广泛接受的假设，即其螺旋细胞形状增强了胃的定植。我们最近首次通过对四个细胞形状决定基因(csd1、csd2、csd3、ccma)的表征为这一理论提供了实验支持，这些基因通过细胞壁肽聚糖(PG)交联的变化促进螺旋细胞的弯曲和扭曲，并且是有效的胃定植所必需的。PG球囊内的多肽交联物的变化为细菌细胞形状的产生定义了一种新的机制；以前的研究描述了作为直杆和曲杆形状的驱动因素的新PG沉积的局部沉积和限制。虽然上述突变体失去了螺旋扭曲，但它们保留了一些曲率。因此，在幽门螺杆菌中产生螺旋形状的确切分子机制仍有许多有待了解。这笔赠款建立在我们已发表的工作的基础上，目的是阐明幽门螺杆菌的螺旋形状生成程序以及该细胞形状程序对幽门螺杆菌致病机制的贡献。目标1将鉴定和鉴定与螺旋细胞形状决定有关的其他基因。目标2将通过对细胞形状蛋白和PG细胞壁组成的生化研究来研究这些基因如何共同作用来促进形状。目的3将研究螺旋细胞形状生成程序促进胃定植的可能机制，包括调节游泳行为和胃内的生态位利用。细菌表现出令人印象深刻的多样性的细胞形状，这些细胞形状在物种内高度保守，但导致特定形状保守的选择性力量却鲜为人知。我们已经建立了一个很好的模型来阐明螺旋细胞形状的分子决定因素和形状在变形杆菌宿主定植过程中的选择作用；CSD蛋白和CCMA同源物在弯曲到螺旋变形杆菌中保存得很好，包括其他几种病原体，如空肠弯曲杆菌和霍乱弧菌。胃定植所需的螺旋形状生成程序的阐明有望阐明抗菌药物设计的新靶点，这些新靶点是幽门螺杆菌迫切需要的，因为目前的菌株对现有疗法显示出越来越多的耐药性，并符合NIAID了解和治疗感染性疾病的使命。 与公共卫生相关：很明显，幽门螺杆菌是一种螺旋状的杆状细菌，在人类胃中定植，会导致从轻度胃炎到消化性溃疡和胃癌的一系列临床结果。我们发现了通过改变细胞壁中肽的交联度来促进螺旋细胞形状的基因。研究这些细胞壁修饰如何促进螺旋细胞形状和细菌在其利基中生活的能力，将有助于我们更好地了解这种细菌是如何致病的，并发现抑制感染的新方法。

DESCRIPTION (provided by applicant): Helicobacter pylori is a helical rod shaped bacterium that colonizes the human stomach causing clinical outcomes that range from mild gastritis to peptic ulcer and gastric cancers. Most descriptions of H. pylori virulence include the widely-accepted hypothesis that its helical cell shape enhances colonization of the stomach. We recently provided the first experimental support for this theory with the characterization of four cell shape determining genes (csd1, csd2, csd3, ccmA) that promote helical cell curvature and twist through changes in cell wall peptidoglycan (PG) crosslinking and are required for efficient stomach colonization. Alteration of peptide crosslinking within the PG sacculus defines a new mechanism for bacterial cell shape generation; previous studies delineated localized deposition and restriction of new PG deposition as drivers of straight rod and curved rod shapes. Though the mutants described above have lost helical twist, they retain some curvature. Thus much remains to be learned about the precise molecular mechanisms for generating helical shape in H. pylori. This grant builds on our published work with a goal of elucidating the H. pylori helical shape generating program and the contributions of this cell shape program to H. pylori pathogenesis. Aim 1 will identify and characterize additional genes involved in helical cell shape determination. Aim 2 will investigate how these genes work together to promote shape using biochemical studies of cell shape proteins and PG cell wall composition. Aim 3 will investigate possible mechanisms by which the helical cell shape generating program promotes stomach colonization including modulation of swimming behavior and niche utilization within the stomach. Bacteria manifest an impressive diversity of cell shapes that are highly conserved within species but the selective forces leading to conservation of specific shapes are poorly understood. We have established H. pylori as an excellent model to elucidate molecular determinants of helical cell shape and the selective role of shape during host colonization in the Proteobacteria; Csd proteins and CcmA homologues are well conserved among curved to helical Proteobacteria including several other pathogens such as Campylobacter jejuni and Vibrio cholerae. The elucidation of a helical shape generating program required for stomach colonization promises to illuminate new targets for antimicrobial design which are badly needed in H. pylori as current strains display increasing resistance to existing therapies and fits the mission of NIAID to understand and treat infectious diseases. PUBLIC HEALTH RELEVANCE: Evident in its name, Helicobacter pylori is a helical rod shaped bacterium that colonizes the human stomach causing clinical outcomes that range from mild gastritis to peptic ulcer and gastric cancer. We discovered genes that promote helical cell shape by altering the extent of peptide crosslinking in the cell wall. Study of how these cell wall modifications promote helical cell shape and the ability of the bacterium to live in its niche will help us better understand how this bacteria causes disease and uncover new ways to inhibit infection.