FIG. 6.

The effects of Mg²⁺, acid, phoP, and pmrA on the expression of pagA and psiD (pmrC). Cells were grown in N medium (pH 7.7) supplemented with 1% vitamin-free Casamino Acids to mid-log phase (2 × 10⁸ cells/ml) in either 10 mM (H) or 10 μM (L) MgSO₄. As indicated below each bar, the cells were adapted at pH 5.8 for 60 min or underwent a stepwise adaptation at pH 5.8 for 30 min followed by 30 min at pH 4.9. The results are representative of triplicate experiments. (A) pagA-lac (JF3303), pagA-lac phoP (JF3531), and pagA-lac pmrA (JF3547) cells; (B) psiD-lac (JF3550), psiD-lac phoP (JF3554), and psiD-lac pmrA (JF3561) cells.