Increased pspF expression is sufficient to mediate increased cell survival at high pH. (A) Wild-type (KW72), ssrS1 (GS075), ΔpspF (KW448), or ΔpspFssrS1 (KW449) cells containing pKK* (open bars) or pKK-pspF* (shaded bars) were inoculated into LB pH 9.3 medium and grown at 37°C for 48 h. Cell densities were measured by plating. Data shown are averages of two experiments with two duplicates each. (B) Wild-type (KW72), ssrS1 (GS075), ΔpspF (KW448), or ΔpspFssrS1 (KW449) cells containing either no plasmid (open bars), pKK-6S* (solid bars), or pKK-pspF* (shaded bars) were tested for sensitivity to 10 M NaOH using the zone-of-inhibition assay. Measurements indicate the diameter of the cell-free zone surrounding the disk. Data shown are from one representative experiment with three duplicate cultures. Similar results were obtained from seven independent experiments. Error bars, standard deviations from the averages.