Effect of carbon source and extracellular pH on the acidification of the culture medium and phosphatase excretion in Neurospora crassa

Exogenous Ca2+ at concentrations up to 3.5 mM increases the sucrose-induced acidification of the culture medium when the mold Neurospora crassa is grown on low-phosphate (Pi) medium at pH 7.8. Induction depends on the pH of the culture medium adjusted for conidial inoculation and on the absence of carbon sources generating cytoplasmic acetyl CoA. Furthermore, the excretion of Pi-repressible acid and alkaline phosphatases was not stimulated by increasing exogenous Ca2+ levels. We also provide evidence that the extracellular pH monitoring by Neurospora crassa may be a determinant in the selective excretion of Pi-repressible acid and alkaline phosphatases.