FIG. 3.

Survival rates after phosphate buffer starvation, hydrogen peroxide exposure, and heat shock exposure of the two subpopulations isolated from an LB medium culture of E. coli incubated for 10 h. Bacteria were separated by ultracentrifugation in the radioselectan solution. (A) Ten milliliters of phosphate buffer was initially inoculated with 10⁷ bacteria/ml. The experiments were repeated six times. (B and C) Ten milliliters of phosphate buffer was initially inoculated with 10⁸ bacteria/ml and exposed to 60°C (B) or 8.8 mM H₂O₂ (C). The experiments were repeated 12 times. Samples were taken at intervals. Culturable bacteria were assayed by plating samples from suspensions onto LB agar plates after serial dilution in cold phosphate buffer. Colonies were counted after 48 h of incubation at 37°C. Symbols: ▪, HD bacteria; •, LD bacteria.