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

项目摘要/摘要 微生物群落对动物生物学和人类健康产生重大影响，并对其造成破坏 社区与多个疾病状态相关。到目前为止，微生物组研究领域一直是 以微生物群落组成的调查和与宿主的组成相关的分析为主 表型。但很少有人尝试将决定因素的具体因果过程直接联系起来 寄主相关细菌的定植动态和成功，以及这些相互作用最终如何影响 主持人。拟议的研究计划的动机是需要实验系统来识别 控制寄主相关细菌群落的组成和后果的机制。这 工作重点放在两个模型系统上，这两个模型系统提供了检查主机关联的补充方法 这为查明宿主殖民的基础机制提供了新的机会。 蜜蜂及其专门的肠道微生物区系为多物种肠道提供了一个特殊的模型。 群落，因为它与人类肠道微生物区系有许多相似之处。在人类和蜜蜂的肠道中，一种马厩， 健康的群落赋予“殖民抵抗力”，即排斥外来微生物；在这两者中 系统的破坏可能导致非典型群落的失调和扩大，包括肠道病原体。 人类的系统非常复杂，不适合进行实验，但对于蜜蜂的内脏来说，我们能够 培养所有组成细菌的分离物，并将其引入无微生物区系的宿主，以建立 定义的社区。我们已经开发了基因工具，用于实验操作优势基因 物种。一组实验将确定决定定殖性的直接宿主-细菌相互作用 特定品系的成败，这些品系对蜜蜂的定植能力各不相同。的现有结果。 诱变筛选表明，外细胞膜的特征在寄主过程中起着至关重要的作用 殖民，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 主持人。除了阐明使特定的细菌菌株能够在特定的 第二组实验将调查微生物菌株之间的相互作用，哪些范围 从代谢的相互依赖到毒素介导的直接拮抗，决定了群落的成员资格。 豌豆蚜虫及其内共生体为细胞内细菌如何相互作用提供了有效的模型。 稳定地定植宿主细胞。我们新设计的技术允许隔离、操作和主机间传输 内生共生菌。为了解决宿主如何控制内共生菌的复制和持久性，我们将执行 基因组比较，生物化学实验，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特征。 通过专注于提供与宿主相关的细菌的易于处理的例子的实验模型，这项工作 将阐明细菌共生体定植宿主能力的基础机制。

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.