Molecular characterization of mixed-species bacterial biofilms in the gastrointestinal tract

肠道微生物区系(定植于胃肠道的微生物群落)在人类健康和疾病中发挥着重要作用，但人们对脊椎动物肠道宿主-微生物共生相互作用的基本原理知之甚少。特别是，对多物种肠道生物膜细菌成员之间的相互作用根本没有研究，但这种知识对于制定调节肠道微生物区系以改善健康的策略是必不可少的。利用诺生菌小鼠(具有特定微生物区系的小鼠)，申请人的团队开发了一种独特的模型，通过该模型可以解开导致胃肠道生物膜形成的细菌功能。利用这个模型，我们已经证明了小鼠胃中选择性生物膜的形成是促进雷氏乳杆菌宿主专一性的关键机制，并开始阐明生物膜形成的分子过程。然而，我们对这些生物膜如何在自然界中出现的混合物种种群的背景下发挥作用和进化知之甚少。*本研究计划的长期目标是确定多物种乳杆菌生物膜进化和作用的机制，并在分子水平上表征单个成员之间的相互作用。在拟议的研究中，我们将使用具有定义的乳杆菌种群的小鼠实验和基因组方法的创新组合，专门识别肠道混合物种生物膜之间的细菌相互作用。该项目的创新之处在于，它使用了共存于野生小鼠肠道中的乳杆菌分离株，一种强大的基因组方法(转座子测序)，它允许直接在环境中识别相关基因，以及一种实验模型(灵生小鼠)，它允许在现实生活的生态环境中研究基因功能。因此，这些实验可能会识别出对细菌生物膜有贡献的基因，这些基因到目前为止还没有被描述过。*对研究领域和加拿大的好处：这项工作可能会对自然界中混合物种细菌生物膜的建立机制以及成员如何进化提供前所未有的洞察，并可能发现在其他生物膜模型中仍然难以捉摸的新过程。这些发现有可能为调整生物膜对人类和动物健康既有益又有害的策略提供基础。该项目将培训六名HQP，其中三人拥有加拿大公民身份或永久居留权，并将提供独特的跨学科经验，使他们具有独特的资格，为肠道微生物群领域(该领域目前被认为是生物学和医学的前沿之一)的进步做出贡献。

The gut microbiota (the community of microbes that colonizes the gastrointestinal tract) plays important roles in human health and disease, but little is known about the basic principles that underlie host-microbial symbiotic interactions in the vertebrate gut. In particular, the interactions between the bacterial members of multi-species intestinal biofilms have not been studied at all, but such knowledge is essential for the development of strategies that modulate the gut microbiota to improve health. Capitalizing on gnotobiotic mice (mice with a defined microbiota), the applicant's group has developed a unique model by which to disentangle the bacterial functions that contribute to biofilm formation in the gastrointestinal tract. Using this model, we have demonstrated that selective biofilm formation in the mouse stomach as a key mechanism by which host specificity is facilitated in the species Lactobacillus reuteri, and have begun to elucidate the molecular processes that underlie formation of biofilms. However, we know little about how these biofilms function and evolve in the context of the mixed species populations that occur in nature. ******The long-term objective of this research program is to identify the mechanisms by which multi-species Lactobacillus biofilms evolved and function, and characterize the interactions between the individual members on a molecular level. In the proposed study, we will use an innovative combination of experiments with mice that harbor defined Lactobacillus populations and genomic approaches to specifically identify bacterial interactions among mixed-species biofilms in the intestinal tract. The project is innovative in that it uses Lactobacillus isolates that coexisted in the gut of wild mice, a powerful genomic approach (transposon sequencing) that allows the identification of relevant genes directly in the environment, and an experimental model (gnotobiotic mice) that allow to study gene function in real-life ecological context. The experiments are therefore likely to identify genes that contribute to bacterial biofilms that have not been described so far.******The benefit to the research field and Canada: The work will likely provide unprecedented insight into the mechanisms by which mixed-species bacterial biofilms in nature are established and how the members evolve, and it is likely to discover novel processes that remain elusive in other models of biofilms. The findings have the potential to provide the basis for strategies to modulate biofilms with both beneficial and detrimental roles in human and animal health. The project will train six HQP, three of which have citizenship or permanent residency in Canada, and will provide a unique interdisciplinary experience that makes them uniquely qualified to contribute to progress in the gut microbiome field (a field that is currently considered one of the frontiers in biology and medicine).