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-in duced acidification of the culture medium when the mold Neurospora cra ssa 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. F urthermore, the excretion of Pi-repressible acid and alkaline phosphat ases was not stimulated by increasing exogenous Ca2+ levels. We also p rovide evidence that the extracellular pH monitoring by Neurospora cra ssa may be a determinant in the selective excretion of Pi-repressible acid and alkaline phosphatases.