FIG. 5.

Influence of external pH on cytoplasmic pH. (A) Growth of mycelium at 30°C in liquid minimal media with defined pH values. Eighteen hours after spore inoculation (10⁶ spores ml⁻¹), mycelia were collected and their biomass was determined gravimetrically after the washed mycelia were dried at 105°C to a constant weight. (B) The average cytoplasmic pH values with representative ratio images from growing hyphae expressing RaVC from the periphery of 18-h-old cultures grown in minimal media with pH values between 2.5 and 9.5. Cytoplasmic pH values were calculated from the fluorescence ratios using the in situ calibration, and the pseudocolors selected represent cytoplasmic pH values between 7.5 and 7.7. Mean cytoplasmic pH values (± standard deviations) for each ratio image also are shown. Bar = 10 μm.