FIG. 4.

SMU.1297 is not required for general stress tolerance in S. mutans. (A) Acid stress. Dilutions of fresh overnight cultures were spotted on THY agar plates in the absence (THY) or presence of sodium citrate buffer to generate a pH of 5.5 to mimic acid stress; the pH 7.0 culture served as a control. (B) Oxidative and thermal stress. Cultures were prepared and spotted as described above, on THY plates containing 1 mM hydrogen peroxide (H₂O₂), for oxidative stress, or on plates containing 0.75 μg/ml puromycin (PU), for thermal stress. Plates were incubated overnight under microaerophilic conditions at 37°C. Experiments were repeated at least three times, and the relevant areas of the representative plates are shown.