Figure 4.

B. subtilis enables S. mutans attachment to hydroxyapatite discs in the presence of casein proteins. Either mono- or dual-species cultures of S. mutans were seeded on hydroxyapatite discs in BHI supplemented with 3% lactose with or without addition of the casein protein mixture (2%). After 24 h of incubation at 37 °C in 95% air/5% CO₂, the discs were washed twice and fixed with 4% formaldehyde. The samples were taken for visualization under SEM. The pictures represent the mono-species biofilm formed by S. mutans (upper panel) and the dual-species biofilm of S. mutans and B. subtilis (lower panel) in the presence of 3% lactose (right) and 3% lactose with addition of the mixture (left).