Synergy between the periodontal pathogens Tannerella forsythia and Porphyromonas gingivalis enhances host inflammatory signaling to polymicrobial biofilms and induces transcriptomic remodeling in T. forsythia II

Although P. gingivalis is considered the keystone pathogen of periodontitis, how its synergistic interaction with the red-complex pathogen Tannerella forsythia shapes biofilm community dynamics, host inflammatory responses, and bacterial gene expression remains largely unexplored. Using a five-species commensal biofilm model, we show that co-introduction of P. gingivalis triggers a greater than 10-fold increase of T. forsythia cell numbers, fundamentally restructuring the microbial community composition.

Combined biofilm challenge induced upregulation of 47 genes in human periodontal ligament mesenchymal stromal cells, predominantly within the TNF and NF-κB signaling pathways, far exceeding inflammatory responses elicited by either pathogen alone. Strikingly, T. forsythia underwent sweeping transcriptomic remodeling in dual-species biofilms—upregulating nutrient acquisition systems, virulence factors, and lanthipeptide biosynthetic gene clusters—whereas P. gingivalis exhibited only minor transcriptomic changes.