Synthetic Mucins as Glycan-Defined Prebiotics.

The human microbiome contains at least as many bacterial cells as human cells. Some bacteria offer benefits, like improving gut barrier function, suppressing pathobiont growth, and modulating immunity. These benefits have popularized probiotics, but probiotic retention is often hindered by low colonization efficiency in the mucosal layer that lines all epithelial cells. Mucins, the primary components of mucus, are essential for the organization and regulation of microbial populations. The molecular mechanisms of mucin-probiotic interactions remain understudied due, in part, to the inability to incisively manipulate native mucin sequences or their glycans. Here, we used synthetic mucins with defined glycan presentations to interrogate glycan-dependent interactions between mucus and three probiotic lactobacilli species. The nutrient conditions under which bacteria were cultured influenced glycan binding preferences, suggesting mucin-probiotic interactions change with nutrient availability. The addition of synthetic mucins to native mucin increased Limosilactobacillus fermentum adherence. Additionally, an increase in glycosidase activity indicated that native and synthetic mucins function as prebiotics, as probiotic bacteria can cleave the displayed O-glycans. Thus, synthetic mucins can cultivate target probiotic bacteria and increase adhesion as binding sites, highlighting their value as tools for elucidating native mucin functions and as promising agents for promoting human health.