Vibrio fischeri as a model of bacterial colonization

许多动物上皮组织是由良性的、通常是必需的细菌共生体定植的，例如那些在口腔和沿着肠道和呼吸道内衬细胞的顶端表面的细菌。这些组织位于环境和身体之间的界面，也是许多细菌性病原体（例如，流感嗜血杆菌和脑膜炎奈瑟菌）感染的部位。在致病性和合作性结合中，细菌和宿主细胞最常通过其表面分子的相互作用或通过其他生物活性化合物的分泌进行交流。鱿鱼Euprymna scopes上皮组织与其革兰氏阴性发光细菌伙伴费氏弧菌（Vibrio fischeri）之间的共生模式正被用作表征这些跨区域细胞-细胞相互作用的系统，并为有益和致病动物-细菌关联之间的关键差异提供见解。最近对该系统的研究表明，脂多糖（LPS）是革兰氏阴性菌的主要表面分子，也是哺乳动物对感染细菌产生最剧烈反应的产物，在这种关系的初始阶段，它会引起鱿鱼宿主细胞生物学和形态的特异性变化。此外，宿主对LPS反应的表征表明，该分子与共生体输出的蛋白化合物协同作用。这些由费氏弧菌衍生的因子诱导的宿主细胞“行为”类型包括：产生粘液以促进易感组织的定植，以及形态发生程序的开始，将宿主组织从未定植的幼体的形态特征转变为成熟的成体的特征。其他几种已确定的宿主细胞对费氏弧菌的反应也可能受到这些化合物的影响。这个跨学科项目的目标是表征费氏弧菌的生物活性分子，特别是脂多糖和与脂多糖协同工作的肽，在鱿鱼-弧菌结合的早期阶段介导宿主组织反应。本提案的具体目标是：(1)表征野生型V. fischeri LPS和直接从共生中衍生的LPS的结构，以及表征与宿主反应受损相关的特定LPS合成突变体衍生的LPS；(2)确定与LPS协同作用的细菌分子的精确生化特性和活性；(3)确定LPS结构的哪些方面在赋予宿主抗菌肽抗性方面发挥作用。

Many animal epithelial tissues are colonized by benign, often essential, bacterial symbionts, such as those in the oral cavity and along the apical surfaces of the cells lining the intestinal and respiratory tracts. These tissues, which occur at the interface between the environment and the body, are also the sites of infection by many bacterial pathogens (e.g., Haemophilus influenzae and Neisseria meningitidis). In both pathogenic and cooperative associations the bacteria and host cells communicate most commonly through interactions of their surface molecules or through the secretion of other bioactive compounds. The model symbiosis between the epithelial tissues of the squid Euprymna scolopes and its Gram-negative, luminous bacterial associate Vibrio fischeri is being exploited as a system by which to characterize these cross-Domain cell-cell interactions and to provide insight into the critical differences between beneficial and pathogenic animal-bacterial associations. Recent studies of this system have shown that lipopolysaccharide (LPS), the principal surface molecule of Gram-negative bacteria and the product responsible for the most dramatic mammalian responses to infective bacteria, induces specific changes in the squid host's cell biology and morphology during the initial stages of the relationship. In addition, characterization of host responses to LPS has revealed that this molecule works synergistically with proteinaceous compounds exported by the symbiont. The types of host cell 'behaviors' induced by these V. fischeri-derived factors include: the production of mucus to facilitate colonization of susceptible tissues, and the onset of a morphogenetic program that transforms host tissues from a morphology characteristic of the uncolonized juvenile to one characteristic of the mature, adult association. Several other identified responses of host cells to V. fischeri may also be affected by these compounds. The goal of this interdisciplinary project is to characterize bioactive molecules of V. fischeri, specifically LPS and the peptides that work in concert with LPS, that mediate host tissue responses during the early phases of the squid-vibrio association. The specific aims of this proposal are to: (1) characterize the structures of wild-type V. fischeri LPS and the LPS derived directly from the symbiosis, as well as characterize LPS derived from specific LPS-synthesis mutants that are associated with compromised host responses; (2) determine the precise biochemical identity and activity of bacterial molecules that act synergistically with LPS; and, (3) determine what aspects of LPS structure play a role in conferring resistance to host antimicrobial peptides.