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Hydrogen peroxide killing and methyl viologen challenge assays.
(A) Panel shows survival rates of S. mutans UA159 (diamonds), TW239 (squares), TW263 (triangles) and JB314 (circles) biofilms after hydrogen peroxide treatment for 90 minutes at room temperature. Biofilms were grown in 50 mL tubes on sterile glass slides in BMGS. Symbols # and * indicate differences between UA159 and the particular mutant at significant level of P<0.01 and 0.001, respectively. (B) Panel B shows growth curves of S. mutans strain grown in BHI in the presence of 10 mM methyl viologen (also paraquat). Strain labels are the same as in panel (A).