Fig. (2) Survival of wild type and mutant S. marcescens strains following ozone (5 ppm) exposure. S. marcescens strains were incubated for either 6h or 48h prior to ozonation. No significant differences were observed among strains in stationary phase (48h) or among strains in exponential phase (6h), but survival was significantly greater (P < 0.05) for exponential-phase cultures compared to stationary-phase cultures.