Fusobacterium bacteriophage FNU1 disrupts complex periodontal pathogenic biofilms comprising Fusobacterium polymorphum, Porphyromonas gingivalis, Tannerella forsythia and Prevotella intermedia.

BACKGROUND: Periodontitis is a chronic inflammatory disease affecting more than 50% of the global population, resulting in irreversible gum damage, alveolar bone loss and ultimately tooth loss. Periodontitis arises from stable, multi-species biofilms whose pathogenicity is driven by emergent ecological interactions persistent to antimicrobial perturbations. Fusobacterium spp. are considered key microbial components that provide scaffolding for this ecological niche, which includes the pathobionts Tannerella forsythia, Prevotella intermedia and Porphyromonas gingivalis. OBJECTIVES: To examined how oral microbial interactions shape periodontal biofilms and whether selectively targeting Fusobacterium polymorphum by bacteriophages can disrupt this pathogenic community structure. MATERIALS AND METHODS: In vitro biofilms were established using (i) F. polymorphum, T. forsythia and P. intermedia on their own, (ii) T. forsythia and P. intermedia in dual-species biofilms with F. polymorphum and (iii) four-species complex biofilms involving F. polymorphum, T. forsythia, P. intermedia and P. gingivalis. The biofilms were then exposed to the F. polymorphum-specific bacteriophage FNU1 to assess the ecological impact of targeted viral predation on a single member of the biofilm community. Biofilm formation, spatial organisation and microbial interactions were visualised by confocal laser scanning microscopy using CellTrace™ proliferation assays and live-dead staining. Community biofilm biomass was quantified using 0.1% crystal violet staining. RESULTS: Multi-species biofilms displayed enhanced biomass and increased cell density relative to simpler communities. Disruption of F. polymorphum by bacteriophage FNU1 led to significant reductions in total biofilm biomass and altered cell density in the single-species F. polymorphum biofilm as well as dual- and four-species complex biofilms. CONCLUSION: Our findings support a role for F. polymorphum-specific bacteriophages in destabilising complex biofilms of periodontal pathobionts. They highlight the importance of F. polymorphum in community dynamics in microbial biofilms and that its precision targeting results in ecological perturbation with the potential to reverse dysbiosis in chronic inflammation in periodontitis.