FIG. 4.

Osmotic stress resistance of catalase mutants. Cells were grown in LB broth at 37°C to an optical density at 600 nm of 0.5. Three 10-fold serial dilutions of the cells in LB broth were spotted onto BDT (Bushnell-Hass minimal salt) agar medium containing 0.8 M or 0.9 M KCl (A) or 32% or 34% sucrose (B). The numbers (10⁵, 10⁴, and 10³) indicate the CFU of the cell spots. (C) Complementation of the salt-sensitive phenotype of the katA mutant was performed by introducing pUCP18-derived plasmids (pUCP-KatA and pUCP-KatB) as in Fig. 2A. Dilutions were made in LB broth or in filter (0.2 μm)-sterilized spent culture supernatants from the stationary-phase cultures of either the wild type (+WT s/n) or the katA mutant (+katA s/n) cells and then spotted onto BDT agar medium containing 0.9 M KCl and 200 μg/ml carbenicillin. The numbers indicate the CFU of the cell spots.