Mucin-degrading gut bacteria: context-dependent roles in intestinal homeostasis and disease.

Akkermansia muciniphila, Bacteroides thetaiotaomicron, Mediterraneibacter (formerly Ruminococcus) gnavus, and other mucin-degrading (MD) bacteria play pivotal roles in shaping gut microbial ecosystems, maintaining gut barrier function, and mediating host-microbiota crosstalk. These bacteria influence intestinal homeostasis by modulating epithelial cell differentiation, immune responses, and gut microbiota composition through mucin degradation and the production of bioactive metabolites. Their abundance and functional activities fluctuate dynamically in response to dietary components, host immunity, and environmental factors, resulting in context-dependent effects on gastrointestinal and systemic health. This review summarizes current insights into the ecology and metabolic capabilities of MD bacteria, highlighting their dual roles in metabolic disorders, inflammatory diseases, infection susceptibility, and neuroimmune conditions. Understanding the ecological niches and molecular interactions of MD bacteria offers promising approaches for microbiota-targeted therapies aimed at restoring gut and systemic homeostasis.