Figure 4.

Coaggregation and biofilm formation of T. denticola wild-type, ΔflgE, ΔmotB with P. gingivalis W50. (A) Coaggregation of T. denticola wild-type and mutants with P. gingivalis W50. T. denticola ATCC 33520 and P. gingivalis cells at exponential growth phase were harvested, washed twice with coaggregation buffer and adjusted to A₆₅₀ of 0.5 with the coaggregation buffer. Equal volumes of T. denticola and P. gingivalis cell suspensions were combined. The height of bacterial aggregates was monitored for 7 h. The data are presented as means plus standard deviations (N = 3). (B) Monospecies and dual-species static biofilms of T. denticola ATCC 33520 wild-type, ΔflgE, ΔmotB with P. gingivalis W50. T. denticola and P. gingivalis cells were grown to exponential phase, diluted to A₆₅₀ of 0.15 and grown anaerobically for 5 days in a 12-well plate, either in a monospecies or dual-species culture. The resultant biofilm was stained with crystal violet and the total biomass determined spectrophotometrically. The data are presented as means and standard deviations (N = 23–27) and were analyzed using a Kruskal-Wallis with Conover-Imam test. All values were significantly different (p < 0.05) except between the following pairs: ΔmotB (mono); wild-type (mono) and ΔflgE (dual); as well as wild-type (dual). (C) SEM image of a biofilm containing T. denticola wild type ATCC 35405 (the long thin spirochaete) and P. gingivalis W50 (the grape-like coccobacillus). The image shows the motile T. denticola facilitating expansion of the biofilm microcolonies by forming bridge structures while carrying P. gingivalis.