Fig. 3.

Hydrogen peroxide killing assay. Strep. mutans wild-type, UA159 (▪), BrpB-deficient mutant, JB409 (○), BrpB-complemented strain, JB409C (•), BrpB- and BrpA-deficient double mutant, JB819 (Δ), and BrpB- and BrpA-complemented strain, JB819C (▴), were grown in regular BHI broth, harvested during mid-exponential phase (OD₆₀₀ 0.3), and then washed twice with 0.1 M glycine buffer before being subjected to hydrogen peroxide killing by incubating the cells in 0.1 M glycine buffer with 0.2 % (w/v) hydrogen peroxide for a period of 90 and 110 min. Results showed that BrpB deficiency weakened the ability of the mutants, JB409 and JB819, to withstand hydrogen peroxide stress. Data presented here are representative of three independent experiments with significant difference being indicated by *, P<0.001, and #, P<0.01, as compared to the wild-type under similar conditions.