Synergy between Tannerella forsythia and Fusobacterium nucleatum in biofilm formation.

During dental plaque formation, the interaction of different organisms is important in the development of complex communities. Fusobacterium nucleatum is considered a 'bridge-organism' that facilitates colonization of other bacteria by coaggregation-mediated mechanisms and possibly by making the environment conducive for oxygen intolerant anaerobes. These studies were carried out to determine whether coaggregation between F. nucleatum and Tannerella forsythia is important in the formation of mixed species biofilms. Further, the role of BspA protein, a surface adhesin of T. forsythia, in coaggregation and biofilm formation was investigated. The results showed the development of synergistic mixed biofilms of F. nucleatum and T. forsythia when these bacteria were cocultured. The BspA protein was not involved in biofilm formation. Though BspA plays a role in coaggregation with F. nucleatum, presumably other adhesins are also involved. The synergistic biofilm formation between the two species was dependent on cell-cell contact and soluble components of the bacteria were not required. This study demonstrates that there is a positive synergy between F. nucleatum and T. forsythia in the development of mixed biofilms and that the cell-cell interaction is essential for this phenomenon.