FIGURE 3.

Acidic pH restores cell envelope integrity of amidase mutants. Comparison of the minimum inhibitory concentration (MIC) of Triton-X for indicated mutants when cultured in buffered LB medium at pH 6.9 or 5.2 (wild type [MG1655], ΔamiAB [EAM1379], ΔamiAC [EAM927], ΔamiBC [EAM1381], and ΔamiABC [EAM1385]). Cells were grown to mid-exponential phase (OD₆₀₀ ~ 0.2–0.6) in LB medium at pH 6.9, then sub-cultured into 96-well plates to 1 × 10⁵ CFU/ml in LB medium buffered to either pH 6.9 or 5.2 with varying percentages of Triton-X detergent. Cells were grown with aeration at 37 °C for 20 hr before MIC was determined by visual inspection. Error bars denote standard deviation