Inflammatory bowel disease (IBD), characterised by chronic intestinal inflammation, is hypothesised to arise from the interplay between susceptibility genes, the immune system, environmental factors, and gut microbiota. Akkermansia muciniphila is a symbiotic bacterium that accounts for 1-5% of the human fecal microbiota. This microbe has been hailed as a next-generation probiotic, principally with regards to its plethora of beneficial host interactions, including the ability to influence mucin secretion and strengthen the intestinal barrier. Though a clear-cut role and mechanism by which A. muciniphila influences inflammatory conditions is unknown, evidence indicates this microbe is depleted in IBD, suggesting it may have protective effects that are lost in these conditions. Here, we investigate the role and mechanism of A. muciniphila in intestinal inflammation and its influence on intestinal barrier function by utilizing barrier-disrupting models of colitis, including dextran sulphate sodium (DSS) and Trichuris muris. Though only minor benefits were derived from this microbe in germ-free mice, in specific pathogen-free (SPF) mice, administration of pasteurized A. muciniphila in a DSS recovery model ameliorated inflammation severity and promoted recovery compared to controls. When gavaged prior to DSS administration, both live and pasteurized A. muciniphila failed to diminish inflammatory markers indicating minimal preventative effects. T. muris-infected SPF mice treated with live A. muciniphila showed increased levels of Th2 and anti-inflammatory cytokines, decreased worm burden, and enhanced levels of the mucin, Muc5ac, compared with those receiving control broth or pasteurized bacteria. Further, both live and pasteurized A. muciniphila ameliorated the severity of inflammation in mucin 2 deficient (Muc2-/-) mouse model of spontaneous colitis, indicating that these protective effects are Muc2-independent. These observations provide us not only with an enhanced understanding of the role A. muciniphila plays in the pathogenesis of intestinal inflammatory conditions but also may fuel novel avenues of treatment for those with IBD. / Thesis / Master of Science (MSc) / Akkermansia muciniphila is a bacterium that accounts for 1-5% of the human fecal microbiota and has been shown to stimulate intestinal mucus production and strengthen the gut barrier. Though several studies have linked inflammatory bowel disease (IBD) with decreased levels of A. muciniphila, the precise role of this microbe in gut inflammation is unknown. In this research, we investigate the role of A. muciniphila in gut barrier function and inflammation. Across several experimental models, we find that supplementation with live, and in some cases, pasteurized A. muciniphila, can help curb established inflammation and promote a more anti-inflammatory gut environment. We also identify that these changes are independent of this bacteria’s ability to influence mucin 2, the main building block of intestinal mucus. This study has the potential to both enhance our understanding of microbial influence in intestinal inflammation and may also lead to the development of future treatments for IBD.

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