Living on the edge: Mucus-associated microbes in the colon

The colonic mucus layer acts as a physicochemical barrier to pathogen invasion and as a habitat for mucus-associated microbes. This mucosal microbiome plays a crucial role in moderating mucus production, maintaining barrier integrity, and shaping the host immune response. However, unchecked mucin foraging may render the host vulnerable to disease. To better understand these dynamics in the mucus layer, it is essential to advance fundamental knowledge on how commensals bind to and utilize mucin as well as their interactions with both the host and their microbial neighbors. We present an overview of approaches for surveying mucus-associated bacteria and assessing their mucin-utilizing capacity, alongside a discussion of the limitations of existing methods. Additionally, we highlight how diet and host secretory immunoglobulin A interact with the mucosal bacterial community in the colon. Insights into this subset of the microbial community can guide therapeutic strategies to optimally support and modulate mucosal barrier integrity.