FIG. 6.
Effect of PhoB activation on ompR malT(Con) mutant survival. (A) Deletion of the pst-phoU genes rescues lethality. Growth curve of the WT (black circles) (AJW678), ompR malT(Con) (black diamonds) (AJW3098), ompR malT(Con) pstS (gray diamonds) (AJW3785), ompR malT(Con) pstC (gray triangles) (AJW3783), ompR malT(Con) pstA (gray circles) (AJW3781), ompR malT(Con) pstB (gray squares) (strain AJW3782), and ompR malT(Con) phoU (white triangles) (AJW3780) strains under nonpermissive conditions are shown. Values represent the mean of triplicates, and error bars indicate standard deviations and are shown only when greater than the size of the symbol. (B) Expression of constitutive PhoBCA(E11K) delays death. Growth curves of the ompR malT(Con) mutant (black diamonds) (AJW3098) and the ompR malT(Con) mutant expressing phoBCA(E11K) (white triangles) are shown. For comparative purposes, the growth curve of the suppressed ompR malT(Con) rseA strain (black circles) is included. Values represent the means of triplicates, and error bars indicate standard deviations and are shown only when greater than the size of the symbol. (C) Activation of the PhoB regulon increases alkaline phosphatase activity in the ompR malT(Con) mutant. Cells were grown under nonpermissive conditions and harvested at an OD of approximately 0.3. Alkaline phosphatase activity was measured using p-NPP as a substrate and is expressed as arbitrary units as described in Materials and Methods. Error bars indicate the standard deviations for triplicates.