Figure 3

pH of cytosol and ER of S. cerevisiae during growth, starvation, following a glucose pulse and upon octanoic acid addition. (A and B) S. cerevisiae cells expressing sfpHluorin (blue) or ER-sfpHluorin (red) grown in lf-SCD medium with 0.1 mM methionine (slightly repressible conditions) were reinoculated in fresh lf-SCD with 0.1 mM methionine to an OD₆₀₀ of 0.1. The pH (A) of cytosol and ER and the OD₆₀₀ (B) were analyzed during 6 hours after reinoculation. (C and D) S. cerevisiae cells expressing sfpHluorin (blue) or ER-sfpHluorin (red) were grown into the exponential growth phase in lf-SCD medium without methionine (fully induced conditions), washed and resuspended in lf-SC medium without methionine and without glucose. pH during glucose starvation (C) and after a glucose pulse (2% w/v) after 4 hours of starvation (D) was followed. (E and F) The pH of cytosol (E) and ER (F) was followed after addition of 0 mg L⁻¹ (black), 50 mg L⁻¹ (yellow), 100 mg L⁻¹ (orange) and 150 mg L⁻¹ (red) octanoic acid. Mean and standard deviation of biological triplicates are shown (mean ± s.d.).