FIG. 3.

Acid induction of ompR. (A) Western blot analysis. Cells (UK1) were grown for 18 h in EG minimal medium, washed, and resuspended to 2 × 10⁸ in pH 4.4 EG medium. The cells were harvested at the times indicated and processed for Western blot analysis using anti-OmpR antibody as described in Materials and Methods; 5 μg of protein was added per lane. (B) Northern blot analysis. Cells (UK1, ompR⁺ [lanes 1 to 5 and 7]; JF2757, ompR::MudJ [lane 6]) were grown and acid shocked as for panel A. As a control, stationary-phase UK1 cells were processed as for acid shock but instead of pH 4.4, they were placed in a pH 8 medium (lane 7). At the times indicated, the samples were harvested and processed for Northern blot analysis as described in Materials and Methods; 5 μg of RNA was added per lane. 23S rRNA hybridization was used as a control. +, present; −, absent.