The Outer Surface of Vibrio cholerae

描述（由申请人提供）：细菌的细胞包膜是一个显著的和复杂的结构，保护细菌免受周围环境的影响。革兰氏阴性菌的一个决定性特征是存在一种外膜，该外膜包裹着这些生物的肽聚糖层。虽然内膜由甘油磷脂组成，但外膜是一种独特的不对称双分子层，甘油磷脂局限于内小叶，脂质a是一种独特的糖脂，位于外小叶。脂质A是LPS的脂质部分，将LPS固定在细菌表面。细菌已经进化出各种机制来适应不可预测的、经常是敌对的环境，包括重塑膜结构的策略。通常，这些修饰提供了对哺乳动物先天免疫系统成分的抵抗力，并调节宿主对入侵微生物的识别。LPS的脂质A结构域对人体是有毒的，并通过TLR4-MD2的识别有效地刺激先天免疫系统。许多革兰氏阴性病原体通过改变脂质A结构来逃避宿主检测。此外，脂质A和甘油磷脂的结构改变可以直接影响细菌对宿主抗菌肽等先天免疫效应物的耐药性。本提案的总体目标是揭示霍乱的病原体霍乱弧菌重塑其膜结构的分子机制以及这种重塑在毒力中所起的作用。本课题的具体目标是：(1)对霍乱弧菌LPS修饰促进抗菌肽耐药性的生化和遗传分析；(2)鉴定参与霍乱弧菌LPS中磷酸甘油部分添加的酶；(3)阐明霍乱弧菌磷脂重塑所需的机制；(4)霍乱弧菌膜重构对宿主先天免疫应答的影响。这些目标的完成将直接有助于我们了解脂质重塑/修饰机制如何影响发病机制。最后，从这项工作中不仅可以更好地了解霍乱疾病，而且可以为疫苗开发和产生工程LPS结构的能力提供新的途径，这些结构可以作为潜在的佐剂和/或LPS拮抗剂。

DESCRIPTION (provided by applicant): The bacterial cell envelope is a remarkable and complex structure that guards bacteria from their surrounding environment. A defining feature of Gram-negative bacteria is the presence of an outer membrane that encapsulates the peptidoglycan layer of these organisms. While the inner membrane is composed of glycerophospholipids, the outer membrane is a unique, asymmetric bilayer with glycerophospholipids confined to the inner leaflet and lipid A, a unique saccharolipid, localized to the outer leaflet. Lipid A is the lipid moiety of LPS and anchors LPS to the bacterial surface. Bacteria have evolved various mechanisms to adapt to their unpredictable and often hostile surroundings, including strategies for remodeling their membrane architecture. Often these modifications provide resistance to components of the mammalian innate immune system and modulate host recognition of the invading microorganism. The lipid A domain of LPS is toxic to humans and potent stimulator of the innate immune system through via recognition by TLR4-MD2. A number of Gram-negative pathogens modify their lipid A structure to evade host detection. Additionally, structural alteration of lipid A and glycerophospholipids can directly impact bacterial resistance to innate immune effectors such as host antimicrobial peptides. The overall objective of this proposal is to unravel the molecular mechanisms by which Vibrio cholerae, the causative agent of the disease cholera, remodels it membrane architecture and the role this remodeling plays in virulence. The specific aims of the current proposal are: (1) biochemical and genetic analysis of V. cholerae LPS modifications promoting antimicrobial peptide resistance; (2) characterization of enzymes involved in the addition of phosphoglycerol moieties to V. cholerae LPS; (3) elucidation of machinery required for phospholipid remodeling in V. cholerae; and (4) impact of V. cholerae membrane remodeling on the host innate immune response. The completion of these Aims will directly contribute to our understanding of how lipid remodeling/modification machinery impacts pathogenesis. Finally, from this work will come not only a better understanding of the disease cholera, but new avenues for vaccine development and the ability to generate engineered LPS structures that could serve as potential adjuvants and/or LPS antagonists.