Figure 1.

The bridging function of Fusobacterium nucleatum in biofilm formation. Fusobacterium nucleatum is a bridging organism that has a great ability to bind to many other microorganisms. In the oral cavity, Fusobacterium nucleatum adheres to both early and late colonizers, promoting the coaggregation of periodontal disease-related pathogens. In addition, it can bind to Candida albicans and Clostridioides difficile. RadD is one of the most profoundly studied adhesions of Fusobacterium nucleatum and contributes to the binding between Fusobacterium nucleatum and Candida albicans, Streptococcus cristatus, Streptococcus gordonii, Streptococcus mutans, Actinomyces naeslundii, Porphyromonas gingivalis, and Clostridioides difficile via an arginine-inhibitable method. Several other Fusobacterium nucleatum outer membrane proteins are also vital in bacterial coaggregation and biofilm formation, including Fap2, FomA and CmpA. Moreover, the Fusobacterium nucleatum outer membrane lectin also contributes to dual-species biofilm formation in a galactose-inhibitable method.