Changes in cytoplasmic pH are involved in the cell type regulation of Dictyostelium

The cytoplasmic pH (pHi) of populations of developing Dictyostelium discoideum cells was determined by means of two independent pH null-point methods. Both methods reveal in populations containing 75-80% prespore cells a pHi value of about 0.2 pH units higher than in populations containing 50% prespore cells. During the process of cell type regulation, decreases and increases in the percentage of prespore cells of about 15-20% are accompanied by decreases and increases in pHi of about 0.2 pH units. Abolition of these changes in pHi by means of a weak base or acid also prevents the regulation process. It is concluded that changes in pHi are involved in the prespore cell type regulation in D. discoideum.