FIG 9.

Survival of C. acetobutylicum wild-type, rex-inactivated mutant, and rex-complemented strains after hydrogen peroxide treatment. The strains were grown in P2 minimal medium to an OD₆₀₀ of about 2.0. Then, cells were exposed to 1 mM iron chelator 2,2′-dipyridyl and the indicated concentrations of H₂O₂ or the equal volume of H₂O. After incubation at 37°C for 30 min, the CFU were determined as the survival of cells and normalized to the number obtained for the nonstressed wild type. Data represent means ± standard deviations of values from three independent experiments.