Cl⁻ contents (A) and distribution ratios (B) for S. cerevisiae grown in media containing varying concentrations of Cl⁻. Solid symbols: cells were washed and suspended at A₆₀₀ of 0.05 in media in which all but ∼5 μM Cl⁻ had been replaced by SO₄⁼, and Cl⁻ was added back as Na³⁶Cl (0.001–0.3 mM), plus, for higher concentrations, 0.7–100 mM NH₄Cl, KCl, or NaCl. Suspensions were incubated aerobically 16–20 h at 30°C, and the cellular ³⁶Cl⁻ contents were determined as described in Materials and methods. Unless otherwise indicated the final extracellular pH was 3.5 ± 0.5. Open symbols: cells were grown in APG, washed, and incubated 2 h at 30°C in APG containing various concentrations of ³⁶Cl⁻ before determining cellular ³⁶Cl⁻ contents. The dashed line in B is the distribution ratio predicted from a Nernst distribution, with plasma membrane potential of −120 mV. The solid curves through the data have no theoretical significance. ♦: strain BY4741, YNB, 25 mM K-citrate buffer, final pH 4.4. ▾, ▴: strain BY4741, YNB. •: strain FKY282, YNB. □: SUL1 deletant (BY4741 background), 2 h, APG.