Elucidation of a bacterial cell shape generating program and pathogenic functions

描述（由申请人提供）：幽门螺杆菌是一种螺旋杆状细菌，定植于人体胃中，导致从轻度胃炎到消化性溃疡和胃癌的临床结局。大多数描述H.幽门螺杆菌的毒力包括广泛接受的假设，即其螺旋细胞形状增强了胃的定植。我们最近提供了第一个实验支持这一理论的表征四个细胞形状决定基因（csd 1，csd 2，csd 3，ccmA），促进螺旋细胞的曲率和扭曲，通过细胞壁肽聚糖（PG）交联的变化，并需要有效的胃定植。PG球囊内肽交联的改变定义了细菌细胞形状生成的新机制;先前的研究描绘了作为直杆和弯曲杆形状的驱动器的新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，关于H中产生螺旋形状的精确分子机制还有许多有待了解的地方。幽门。这项资助建立在我们已发表的工作的基础上，目的是阐明H。pylori螺旋形状生成程序以及该细胞形状程序对H. pylori发病机制目的1将确定和表征额外的基因参与螺旋细胞形状的决定。目的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以促进形状。目的3探讨螺旋细胞形状生成程序促进胃定植的可能机制，包括调节胃内的游泳行为和生态位利用。细菌表现出令人印象深刻的多样性的细胞形状是高度保守的物种，但选择力导致特定形状的保护知之甚少。我们建立了H。pylori作为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菌中宿主定殖期间的选择性作用; Csd蛋白和CcmA同源物在弯曲至螺旋变形菌中很好地保守，包括几种其他病原体，如空肠弯曲杆菌和霍乱弧菌。阐明胃定植所需的螺旋形状生成程序，有望阐明新的抗菌设计目标，这是迫切需要在H。幽门螺杆菌作为目前的菌株显示出对现有疗法的抗性增加，并且符合NIAID理解和治疗传染病的使命。 公共卫生相关性：幽门螺杆菌（Helicobacter pylori）是一种螺旋杆状细菌，在人类胃中定植，导致从轻度胃炎到消化性溃疡和胃癌的临床结果。我们发现了通过改变细胞壁中肽交联程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生态位中生存的能力，将有助于我们更好地了解这种细菌如何引起疾病，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.