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

Fusobacterium nucleatumis a common member of the oral microbiota frequently associated with extra-oral 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 betweenF. nucleatumandSegatella 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 orS. orissupernatants modestly enhancedF. nucleatumgrowth, both conditions triggered transcriptional remodeling, including induction of thenanoperon for sialic acid catabolism, suggesting reliance on glycan degradation byS. oris.Conversely,S. orisexhibited differential expression of multiple polysaccharide utilization loci (PULs) when exposed toF. nucleatumor its metabolites. Biofilm formation byF. nucleatumwas strongly inhibited byS. oris,indicative of antagonistic interactions. Dual and triple RNA-seq revealed that epithelial responses were predominately shaped byF. nucleatum,with enrichment of inflammatory and cancer-associated pathways; however, co-colonization withS. orismodulated 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 ofF. nucleatumin mucosal environments. This work underscores the importance of modeling polymicrobial communities under host-relevant conditions to better understand pathobiont behavior at the epithelial interface.