Crossfeeding interactions between Fusobacterium nucleatum and Segatella oris on human airway epithelial cells

Fusobacterium nucleatum is increasingly recognized as a pathobiont in mucosal diseases, including colorectal cancers and chronic airway infections, yet its functional interactions with co-colonizing microbiota remain poorly understood. Here, we demonstrate that F. nucleatum engages in bidirectional interactions with Segatella oris, a glycan-foraging anaerobe also enriched in mucin-rich environments. Through nutrient cross-feeding, antagonism, and transcriptional modulation, these interactions shape bacterial behavior and the host epithelial response. Notably, glycan degradation by S. oris enables F. nucleatum access to sialic acids, while F. nucleatum suppresses expression of multiple polysaccharide utilization loci in S. oris, revealing a reciprocal ecological influence. Co-colonization of the airway epithelial surface also modulates gene expression linked to inflammation and cancer. These findings advance our understanding of polymicrobial dynamics at mucosal interfaces and highlight the importance of incorporating microbe-microbe-host interactions into reductionist models of infection and disease.