The Outer Surface of Vibrio cholerae

描述（由申请人提供）：革兰氏阴性细菌霍乱弧菌被归类为B类食源性和水源性病原体，可引起急性、严重的肠道疾病，称为霍乱。不幸的是，霍乱仍然是发展中国家的一个严重健康威胁，每年发生约300万至500万病例。霍乱弧菌是河口水域环境中的一种常见寄生菌，属于河口水域自由生活的细菌植物群。虽然已知大约200个公认的O血清群，但只有携带脂多糖（LPS）体细胞抗原O 1或O 139的霍乱弧菌菌株与霍乱大流行有关。与大多数革兰氏阴性菌的情况一样，霍乱弧菌的LPS由三个不同的区域组成：膜相关脂质A结构域、短核心寡糖和O-抗原多糖。虽然脂质A结构域是革兰氏阴性细菌膜的重要组成部分，并且通过保守途径合成，但它是一种高度多样化的分子。病原菌响应于其周围环境而修饰其LPS的脂质A结构域。由于脂质A是LPS的生物活性部分，这些修饰可以通过改变经由先天免疫受体复合物TLR 4/MD-2的LPS识别来对疾病产生深远影响。此外，脂质A结构的改变可影响外膜渗透屏障和细菌对宿主抗微生物肽的抗性。我们的总体目标是了解位于细菌表面的LPS结构的改变如何促进霍乱弧菌在水生环境和人类宿主中的存活。该提案将集中于定义响应于细菌的细胞外环境的胆固醇弧菌脂质A的结构改变以及该过程所需的酶机制。将在模拟水生环境或小肠中发现的条件的不同生长条件下监测霍乱弧菌脂质A的结构变化。完成以下目标将大大增加我们对霍乱细菌机制的理解，并可能为开发新疗法和改进疫苗提供目标。当前提案的具体目的是：（i）霍乱弧菌脂质A种类的结构分析;（ii）霍乱弧菌脂质A结构的环境调节;（iii）霍乱弧菌脂质A的酶促修饰;和（iv）霍乱弧菌LPS介导的Toll样受体免疫激活。

DESCRIPTION (provided by applicant): The Gram-negative bacterium Vibrio cholerae is classified as a Category B food- and water-borne pathogen, causing the acute, severe, diarrheal disease known as cholera. Unfortunately, cholera still remains a serious health threat to developing countries with approximately 3-5 million cases occurring annually. V. cholerae is a normal inhabitant of aquatic environments, belonging to the free-living bacterial flora in estuarine areas. Although approximately 200 recognized O serogroups are known, only V. cholerae strains bearing the lipopolysaccharide (LPS) somatic antigens O1 or O139 have been associated with cholera pandemics. As is the case with most Gram-negative bacteria, the LPS of V. cholerae is composed of three distinct regions the membrane associated lipid A domain, a short core oligosaccharide, and the O-antigen polysaccharide. Although the lipid A domain is an essential component of Gram-negative bacterial membranes and is synthesized via a conserved pathway, it is a highly diverse molecule. Pathogenic bacteria modify the lipid A domain of their LPS in response to their surrounding environment. Since lipid A is the bioactive portion of LPS, these modifications can have a profound impact on disease, by altering LPS recognition via the innate immune receptor complex, TLR4/MD-2. Additionally, alteration of the lipid A structure can impact the outer membrane permeability barrier, and bacterial resistance to host antimicrobial peptides. Our overall objective is to understand how alterations in the structure of LPS located on the bacterial surface promote survival of V. cholerae both in the aquatic environment and in the human host. This proposal will focus on defining structural alterations of V. cholerae lipid A in response to the bacterium's extracellular environment and on the enzymatic mechanisms required for this process. Structural alterations of V. cholerae lipid A will be monitored under diverse growth conditions that mimic conditions found either in the aquatic environment or in the small intestine. Completion of the aims below will significantly increase our understanding of the bacterial mechanisms contributing to cholera and possibly provide targets for the development of novel therapies and improved vaccines. The specific aims of the current proposal are: (i) structural analysis of V. cholerae lipid A species; (ii) environmental regulation of V. cholerae lipid A structure; (iii) enzymatic modification of V. cholerae lipid A; and (iv) Toll-like receptor mediated immune activation by V. cholerae LPS.