Abstract
The mechanisms of action of mineral phosphate solubilization (MPS) were studied in the wild-type Mps + Penicillium rugulosum strain IR94-MF1 and in negative (Mps −) and superpositive (Mps ++) mutants derived from it. MPS activities were measured in liquid media using sucrose as C source, four N (arginine, nitrate, nitrate+ammonium and ammonium) and P sources (KH 2PO 4, hydroxyapatite, FePO 4 and AlPO 4). Ammonium significantly ( P<0.01) decreased phosphate solubilization, and this activity was 1–66 times higher in the Mps ++ mutant than in the wild-type depending on the P and N sources used. The Mps + phenotype was strongly associated with the production of gluconic or citric acids. The results also suggest for the MPS − mutant the involvement of the H + pump mechanism in the solubilization of small amounts of phosphates.
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