FIG. 1.

Effect of low pH on expression of the reporter gene PST1-lacZ in wild-type (WT) and rlm1Δ strains. (A) Cells transformed with YEp357R-PST1 were grown at 30°C to an OD₆₀₀ of 0.5 in YNB either in standard minimal medium or in medium buffered at pH 5.5. For each experiment, the culture was divided into two parts. The first culture was kept under standard conditions as an unshocked control. The pH of the second culture was decreased from 5.5 to 3.5 or 2.8 for buffered YNB medium and 3.5 to 2.8 for standard YNB medium. β-Galactosidase activity was measured 4 hours after the low-pH stress as described in Materials and Methods. Results were from three independent assays, and the error bar indicates mean error. (B) Cells transformed with YEp357R-PST1 were grown at 30°C in minimal medium, and β-galactosidase activity was measured during growth. WT (triangles), rlm1Δ (squares).