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棒状细菌，定植在人的胃中，引起从轻度胃炎到消化性溃疡和胃癌的临床结果。大多数关于幽门螺杆菌毒力的描述包括一个被广泛接受的假设，即它的螺旋细胞形状增强了胃的定植。我们最近通过表征四个细胞形状决定基因（csd1, csd2, csd3, ccmA）为这一理论提供了第一个实验支持，这些基因通过改变细胞壁肽聚糖（PG）交联促进螺旋细胞曲率和扭曲，并且是有效的胃定植所必需的。PG小囊内肽交联的改变定义了细菌细胞形状生成的新机制；先前的研究描述了局部沉积和限制新的PG沉积是直杆和弯曲杆形状的驱动因素。虽然上面描述的突变体失去了螺旋扭曲，但它们保留了一些曲率。因此，在幽门螺旋杆菌中产生螺旋形状的精确分子机制仍有待研究。这项资助建立在我们发表的工作的基础上，目的是阐明幽门螺杆菌螺旋形状生成程序和这种细胞形状程序对幽门螺杆菌发病机制的贡献。目的1将鉴定和表征参与螺旋细胞形状决定的其他基因。目的2将研究这些基因如何通过细胞形状蛋白和PG细胞壁组成的生化研究来共同促进形状。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细胞形状多样性，在物种内高度保守，但导致特定形状保守的选择力知之甚少。我们已经建立了幽门螺杆菌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杆菌中宿主定植过程中的选择性作用；Csd蛋白和CcmA同源物在弯曲到螺旋的变形菌中很好地保守，包括一些其他病原体，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幽门螺杆菌急需的抗菌设计新靶点，因为当前菌株对现有疗法的耐药性越来越强，符合NIAID了解和治疗传染病的使命。

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.