FIG. 5.

Changes in oxidative tolerance in S. mutans UA159 when cells are reexposed to oxygen. Cells were grown under aerobic or anaerobic conditions, diluted into fresh BHI broth containing 0.001% hydrogen peroxide (A) or 25 mM paraquat (B), and regrown under anaerobic (overlaid with mineral oil) or aerobic (without mineral oil) conditions. The growth rate of S. mutans was monitored using a Bioscreen C system (solid black line, aerobically grown cells were diluted and regrown under aerobic conditions; dotted black line, anaerobically grown cells were diluted and regrown under aerobic conditions; solid gray line, aerobically grown cells were diluted and regrown under anaerobic conditions; dotted gray line, anaerobically grown cells were diluted and regrown under anaerobic conditions). Data presented here are representative of at least three independent experiments.