Fig 4.

Biofilm formation. S. mutans strains were grown to an OD₆₀₀ of 0.5 in BHI broth, diluted 1:50 in BM semidefined medium supplemented with 10 mM sucrose (A) or with 20 mM glucose (B) in a 96-well microtiter plate, and incubated at 37°C with 5% CO₂ for 48 h. To quantify biofilm formation, the plates were washed twice, stained with 0.1% crystal violet, and resuspended with an ethanol-acetone (8:2 [vol/vol]) mixture. The optical density of the stained biofilm was measured at OD₅₇₅. Data represent the means and standard deviations (error bars) of the results obtained with three separate isolates assayed in triplicate. *, data differ from the wild-type genetic background data at P ≤ 0.001 (Student's t test); **, data differ from the Δpta strain data at P < 0.005. WT, wild type.