T reponema denticola improves adhesive capacities of P orphyromonas gingivalis

P orphyromonas gingivalis , an important etiological agent of periodontal disease, is frequently found associated with T reponema denticola , an anaerobic spirochete, in pathogenic biofilms. However, interactions between these two bacteria are not well understood at the molecular level. In this study, we seek to link the influence of T . denticola on the expression of P . gingivalis proteases with its capacities to adhere and to form biofilms. The P . gingivalis genes encoding Arg‐gingipain A ( RgpA ), L ys‐gingipain ( Kgp ), and hemagglutinin A ( HagA ) were more strongly expressed after incubation with T . denticola compared with P . gingivalis alone. The amounts of the three resulting proteins, all of which contain hemagglutinin adhesion domains, were increased in culture supernatants. Moreover, incubation of P . gingivalis with T . denticola promoted static and dynamic biofilm formation, primarily via a time‐dependent enhancement of P . gingivalis adhesion capacities on bacterial partners such as S treptococcus gordonii . Adhesion of P . gingivalis to human cells was also increased. These results showed that interactions of P . gingivalis with other bacterial species, such as T . denticola , induce increased adhesive capacities on various substrata by hemagglutinin adhesion domain‐containing proteins.