Understanding the impact of the host on microbial ecology and host functions in the gastrointestinal tract of calves using functional genomics

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The mammalian gastrointestinal tract (GIT) harbours dynamic and abundant microbial populations and such populations are rapidly established during and immediately after birth. There is increasing evidence that commensal microbiota plays an important role in the development of the GIT epithelial barrier and host immune functions. However, the understanding of host-microbial interactions in the GIT of cows is limited and its role in animal health has not been well studied. Newborn calves acquire microbes in their GIT from both their mother and the surrounding environment. Recent studies from my laboratory have demonstrated that differences in the mucosa-associated bacterial community resulted in significant variation in expression of innate immune genes. These communities did not simply reflect those associated with digesta indicating that there is a significant host role in establishing these communities. Studies from human and mice have shown that once the microbial community is established - the "footprint" of this community is very difficult to change except temporarily. In turn, the host-microbial interrelationship plays a regulatory role in maintaining gut homeostasis. The mucosal epithelium provides a barrier between the host and the gut environment and it plays a key role in recognizing the GIT microbiome and regulating the passage of microbial byproducts as well as microbial cells, especially pathogens. I propose to investigate the role of the host on host-microbial interactions in the GIT of calves using a functional genomics approach based on the hypothesis that the development of epithelial barrier functions of GIT can be regulated by the host recognition of the microbial colonization and byproducts in the early life of cows. The objectives of this study are 1) to identify an interplay among gut microbiota, the epithelial barrier (tight junctions), and the mucosal immune function, and 2) to identify the effect of diet on the barrier functions related to microbiota in dairy calves using functional genomics analysis. This will contribute to the fundamental knowledge on host-microbial interctions in ruminants and future applications to improve animal gut health for more sustainable animal production in Canada.