Contact-Dependent Antagonism in Gut Bacteroidales

 描述(申请人提供)：人类肠道微生物区系包含超过35种类杆菌目，它们共同是这个微生物生态系统中最丰富的革兰氏阴性细菌。我们对这些肠道细菌如何相互作用以建立促进健康的微生物群落知之甚少。这项应用解决了肠道类杆菌VI型分泌系统(T6SS)介导的拮抗相互作用。直到最近，T6SS只在变形杆菌物种中被描述。我们发现T6SS在肠道类杆菌中含量丰富，并在205个人类肠道类杆菌基因组中确定了114个T6SS基因座。我们已经实验证明，其中两个T6SS介导了与其他类杆菌属物种的拮抗相互作用。这项提案的两个目的是从生态系统的建立、防御、入侵和稳定方面研究与这些T6SS有关的最重要的问题。在目标1中，我们将采用分子方法研究T6SS，它们的细菌靶向范围，毒性效应的鉴定，在一些菌株中观察到的T6SS抗性的基础，以及TetR家族转录抑制因子对T6SS激活的调节。我们还将分析肠道拟杆菌T6SS是否针对肠道病原体，从而有助于微生物群的定植抵抗功能。第二个目的是利用第一个目的中产生的突变体和分子工具，全面研究T6SS介导的拮抗作用在哺乳动物肠道中的相关性。为此，我们将使用诺生菌小鼠肠道定植模型进行实验，以确定T6SS是否促进菌株对已建立的生态系统的入侵，以及T6SS在阻止竞争敏感菌株的定植中的作用。这些研究还将包括分析来自人类肠道生态系统的自然共存菌株之间的T6SS介导的拮抗作用，以确定T6SS介导的拮抗作用是否发生在自然稳定的人类肠道微生物群落中。此外，我们还将研究T6SS通过整合结合元件在体外菌株之间和灵芝小鼠结肠内转移的能力。这些研究将有助于我们理解肠道物种与有助于建立人类肠道微生物生态系统的因素之间的动态相互作用。

 DESCRIPTION (provided by applicant): The human intestinal microbiota contains more than 35 species of the order Bacteroidales, which collectively are the most abundant Gram negative bacteria of this microbial ecosystem. We know very little about how these intestinal bacteria interact with each other to establish health-promoting microbial communities. This application addresses antagonistic interactions mediated by Type VI secretion systems (T6SS) of the gut Bacteroidales. Until recently, T6SS were only described in Proteobacterial species. We have found that T6SS are abundant in the gut Bacteroidales and we have identified 114 T6SS loci in 205 human gut Bacteroidales genomes. We have experimentally demonstrated that two of these T6SSs mediate antagonistic interactions with other Bacteroidales species. The two aims of this proposal are designed to study the most important questions regarding these T6SSs in terms of ecosystem establishment, defense, invasion and stability. In Aim 1, we will take a molecular approach to study the T6SSs, their range of bacterial targeting, identification of toxic effectors, the basis of theT6SS resistance observed in some strains, and regulation of T6SS firing by a transcriptional repressor of the TetR family. We will also analyze if T6SS of gut Bacteroidales target enteric pathogens, thereby contributing to the microbiota's colonization resistance function. The second aim is designed to utilize the mutants and molecular tools that were generated in the first aim to comprehensively study the relevance of T6SS-mediated antagonism in the mammalian gut. For this aim, we will perform experiments using a gnotobiotic mouse intestinal colonization model to determine if T6SSs facilitate the invasion of a strain into an established ecosystem, and the roles of T6SSs in thwarting colonization of competing sensitive strains. These studies will also include analyses of T6SS-mediated antagonism between naturally co- resident strains from a human gut ecosystems to determine if T6SS-mediated antagonism occurs in a naturally stable human gut microbial community. In addition, we will study the ability of T6SS to be transferred by integrative conjugative elements between strains in vitro and within the gnotobiotic mouse colon. These studies will contribute significantl to our understanding the dynamic interactions that occur between gut species and the factors that contribute to the establishment of human intestinal microbial ecosystems.