Vibrio fischeri as a model of bacterial colonization

许多动物上皮组织被良性的、通常是必需的细菌共生体定植，例如口腔中的共生体以及沿肠道和呼吸道衬里细胞的顶端表面的共生体。这些组织发生在环境和身体的交界处，也是许多细菌病原体(如流感嗜血杆菌和脑膜炎奈瑟氏菌)感染的场所。在致病联合和合作联合中，细菌和宿主细胞最常见的是通过表面分子的相互作用或通过分泌其他生物活性化合物进行交流。鱿鱼Euprymna Scolope的上皮组织与其革兰氏阴性发光细菌伴生弧菌之间的模式共生正被用作一种系统，通过它来表征这些跨域细胞-细胞相互作用，并提供对有益和致病动物-细菌联系之间的关键差异的洞察。最近对该系统的研究表明，内毒素是革兰氏阴性细菌的主要表面分子，也是哺乳动物对感染细菌产生最戏剧性反应的产物，在这种关系的最初阶段，它会诱导鱿鱼宿主的细胞生物学和形态发生特殊的变化。此外，宿主对内毒素的反应的表征表明，该分子与共生菌输出的蛋白质类化合物具有协同作用。这些裂隙弧菌衍生的因子诱导的宿主细胞“行为”类型包括：产生粘液以促进敏感组织的定植，以及形态发生程序的启动，该程序将宿主组织从未定植幼体的形态特征转变为成熟、成体联合的特征之一。寄主细胞对费氏弧菌的其他几种已确定的反应也可能受到这些化合物的影响。这一跨学科项目的目标是表征鱼弧菌的生物活性分子，特别是内毒素以及与内毒素协同工作的多肽，这些多肽在鱿鱼-弧菌联合的早期阶段调节宿主组织的反应。这项建议的具体目的是：(1)鉴定野生型和直接来自共生的内毒素的结构，以及鉴定来自与受损宿主反应相关的特定内毒素合成突变体的内毒素；(2)确定与内毒素协同作用的细菌分子的确切生化特性和活性；以及(3)确定内毒素结构的哪些方面在赋予对宿主抗菌肽的耐药性方面发挥作用。

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.