FIG. 1.
Changes in pHi and acetate pool levels upon addition of 8 mM acetate to E. coli Frag1 at pH 6. Acetate (8 mM) was added to E. coli cells growing at pH 6. (a) pHi was determined by the distribution of radioactive benzoate (□), as described in Materials and Methods. (b) Acetate pool levels (•) were determined as described in Materials and Methods. The predicted acetate pool level (◊) based upon a pK of 4.7 for acetate, the free acetate anion concentration outside the cells (7.6 mM), and the pHi determined by benzoate distribution is indicated. The data shown are composites from several independent experiments in which the time courses were overlapped to enable rapid sampling.