FIG. 3.
Changes in growth rate, pHi, and glutamate pool levels upon suspension of acetate-treated cells in acetate-free medium. (a) Cultures were grown to exponential phase in pH 6 medium containing either acetate or benzoate. The growth data for both acetate-treated and benzoate-treated cultures obtained prior to transfer to acid-free medium are represented by a single set of data points (▵). After approximately 3 h of incubation, the cells were rapidly filtered and transferred into pH 6 medium without the weak acid, and the incubation was continued. Symbols: ▪, acetate-treated cells; •, benzoate-treated cells. (b) Cells were pregrown at pH 6 in the presence of 8 mM acetate, and the cytoplasmic pH (□) and glutamate pool levels (•) were determined as described in Materials and Methods. After a 5-min preincubation period, cells were transferred into acetate-free medium, pHo 6, and the changes in pHi and glutamate pool levels were recorded.