Contact-Dependent Antagonism in Gut Bacteroidales

 描述（由申请人提供）：人体肠道微生物群含有超过35种拟杆菌目，它们共同是该微生物生态系统中最丰富的革兰氏阴性菌。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。本申请涉及由肠道拟杆菌目的VI型分泌系统（T6SS）介导的拮抗相互作用。直到最近，T6SS仅在变形菌属中被描述。我们已经发现T6SS在肠道类杆菌中是丰富的，并且我们已经在205个人类肠道类杆菌基因组中鉴定了114个T6SS位点。我们已经通过实验证明，这些T6SS介导的拮抗相互作用与其他拟杆菌目物种。该提案的两个目的是研究这些T6SS在生态系统建立，防御，入侵和稳定性方面的最重要问题。在目标1中，我们将采取分子方法来研究T6SS，它们的细菌靶向范围，毒性效应物的鉴定，在一些菌株中观察到的T6SS抗性的基础，以及TetR家族的转录阻遏物对T6SS发射的调节。我们还将分析肠道类杆菌的T6SS是否靶向肠道病原体，从而有助于微生物群的定植抗性功能。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来全面研究哺乳动物肠道中T6SS介导的拮抗作用的相关性。为了这个目的，我们将使用一个gnotobiotic小鼠肠道定植模型进行实验，以确定T6SSs是否有助于菌株侵入已建立的生态系统，以及T6SSs在阻碍竞争敏感菌株定植中的作用。这些研究还将包括对来自人类肠道生态系统的天然共存菌株之间的T6SS介导的拮抗作用的分析，以确定T6SS介导的拮抗作用是否发生在天然稳定的人类肠道微生物群落中。此外，我们将研究T6SS在体外和在gnotobiotic小鼠结肠内通过菌株之间的整合接合元件转移的能力。这些研究将有助于我们理解肠道物种之间发生的动态相互作用以及有助于建立人类肠道微生物生态系统的因素。

 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.