Elucidating the molecular bases of species interactions in host-associated bacterial communities

项目总结/摘要 微生物群落对动物生物学和人类健康产生重大影响， 社区与多种疾病状态相关。到目前为止，微生物组研究领域已经 以微生物群落组成调查和分析与宿主相关的组成为主 表型但是，很少有人试图将决定性的具体因果过程直接联系起来， 宿主相关细菌的定植动力学和成功，以及这些相互作用最终如何影响 hosts.拟议的研究计划的动机是需要实验系统，以确定 控制宿主相关细菌群落的组成和后果的机制。这 工作集中在两个模型系统，提供互补的方法来检查主机相关的 社区，并提供新的机会，以确定潜在的主机殖民化的机制。 蜜蜂及其专门的肠道微生物群为多物种肠道提供了一个特殊的模型 因为它与人类肠道微生物群有许多共同特征。在人类和蜜蜂的肠道中， 健康的社区赋予“殖民抵抗力”，排除外来微生物;在这两个 如果系统受到破坏，可能导致生态失调和非典型群落的扩大，包括肠道病原体。 人类的系统非常复杂，不适合实验，但是，对于蜜蜂的肠道，我们能够 培养所有组成细菌物种的分离株，并将其引入无微生物群的宿主， 定义的社区。我们已经开发出了遗传工具，用于实验性地操纵占优势的 物种一组实验将确定决定定植的宿主-细菌直接相互作用 成功或失败的特定菌株，不同的能力殖民蜜蜂。现有成果来自 诱变筛选表明，外细胞被膜特征在寄主过程中起重要作用 殖民化，我们将使用新的遗传工具来确定这些因素中的哪些是接受的关键。 hosts.除了阐明使特定细菌菌株能够单定殖特定细菌的机制之外， 宿主，第二组实验将研究微生物菌株之间的相互作用， 从代谢共依赖性到直接毒素介导的拮抗作用，确定群落成员。 豌豆蚜及其内共生菌为研究胞内细菌如何缔合提供了一个有效的模型 稳定地定殖宿主细胞。我们新设计的技术允许分离，操纵和宿主间转移 内共生体为了解决主机如何控制内共生体复制和持久性，我们将执行 基因组比较，生化实验，以测试宿主产生的基因产物对 内共生体细胞，以及内共生体外膜蛋白的物理和结构表征。 通过专注于实验模型，提供宿主相关细菌的易处理的例子，这项工作 将阐明细菌共生体在宿主中定植能力的机制。

Project Summary/Abstract Microbial communities exert major impacts on animal biology and human health, and disruption of these communities is associated with multiple disease states. To date, the field of microbiome research has been dominated by surveys of microbial community compositions and by analyses correlating composition with host phenotypes. But there have been few attempts to directly link the specific, causal processes that determine colonization dynamics and success of host-associated bacteria, and how these interactions ultimately affect hosts. The proposed research plan is motivated by the need for experimental systems to identify the mechanisms that control the composition and consequences of host-associated bacterial communities. This work focuses on two model systems that provide complementary approaches to examining host-associated communities, and that offer new opportunities to identify the mechanisms underlying host colonization. The honey bee and its specialized gut microbiota provides an exceptional model for multispecies gut communities as it shares many features with the human gut microbiota. In both human and bee guts, a stable, healthy community bestows “colonization resistance”, the exclusion of foreign microorganisms; in both systems, disruption can result in dysbiosis and expansion of atypical communities, including enteric pathogens. The human system is highly complex and not amenable to experiments, but, for the bee gut, we are able to culture isolates of all component bacterial species and to introduce these to microbiota-free hosts to establish defined communities. We have already developed genetic tools for experimental manipulation of the dominant species. One set of experiments will identify the direct host-bacterial interactions that determine colonization success or failure of particular strains that vary in ability to colonize honey bees. Existing results from a mutagenesis screen indicate that features of the outer cell envelope play essential roles during host colonization, and we will use new genetic tools to determine which of these factors are key to acceptance by hosts. In addition to elucidating the mechanisms that enable specific bacterial strains to mono-colonize specific hosts, a second set of experiments will investigate how the interactions between microbial strains, which range from metabolic co-dependency to direct toxin-mediated antagonism, determine community membership. The pea aphid and its endosymbionts provide an effective model for how intracellular bacterial associates stably colonize host cells. Our newly devised techniques allow isolation, manipulation and inter-host transfer of endosymbionts. To address how hosts control endosymbiont replication and persistence, we will perform genomic comparisons, biochemical experiments to test effects of host-produced gene products on endosymbiont cells, and physical and structural characterization of endosymbiont outer membrane proteins. Through focus on experimental models that provide tractable examples of host-associated bacteria, this work will illuminate the mechanisms that underlie ability of bacterial symbionts to colonize hosts.