FIG 7.

Exogenous ROS can eliminate nalidixic acid-mediated paradoxical survival. Exponentially growing cultures of wild-type E. coli (strain 3505) were treated for 2 h with the indicated concentrations of nalidixic acid (Nal), and survival was measured as described in Materials and Methods (squares). In a parallel culture, hydrogen peroxide (H₂O₂), at a sublethal final concentration of 2 mM, was added to cultures for an additional 20 min (circles). Data represent the means from three independent experiments; error bars represent standard errors of the mean.