Cross-feeding interactions between Fusobacterium nucleatum and the glycan forager Segatella oris

Fusobacterium nucleatum is a common member of the oral microbiota frequently associated with extraoral infections and diverse polymicrobial environments, including chronic airway diseases and colorectal tumors. Yet, its interactions with co-colonizing microbiota remain poorly defined. Here, we investigate cross-feeding interspecies dynamics between F. nucleatum and Segatella oris, a glycan-foraging anaerobe enriched in airways and gastrointestinal tumors. Using broth cultures, cell-free supernatants, and co-culture on primary human airway epithelial cells, we identify bidirectional interactions that shape nutrient acquisition, biofilm formation, gene expression, and host responses. While mucin or S. oris supernatants modestly enhanced F. nucleatum growth, both conditions triggered transcriptional remodeling, including induction of the nan operon for sialic acid catabolism, suggesting reliance on glycan degradation by S. oris. Conversely, S. oris exhibited differential expression of multiple polysaccharide utilization loci (PULs) when exposed to F. nucleatum or its metabolites. Biofilm formation by F. nucleatum was strongly inhibited by S. oris, indicative of antagonistic interactions. Dual and triple RNA-seq revealed that epithelial responses were predominately shaped by F. nucleatum, with enrichment of inflammatory and cancer-associated pathways; however, co-colonization with S. oris modulated the magnitude and specificity of host gene expression. These findings demonstrate that glycan-mediated cross-feeding and microbial interactions shape the physiology and pathogenic potential of F. nucleatum in mucosal environments. This work underscores the importance of modeling polymicrobial communities under host-relevant conditions to better understand pathobiont behavior at the epithelial interface.