SOLUBILIZATION OF INORGANIC PHOSPHATES BY MICROORGANISMS ISOLATED FROM FOREST SOILS

Two strains (a Penicillium sp. and a Pseudomonas sp.) having high abilities to solubilize inorganic phosphates (hydroxylapatite and calcium hydrogenphosphate dihydrate) were screened from 600 colonies isolated from forest soils. Some of their physiological properties (nutrition, O2-demand, temperature) were investigated. It was possible to distinguish between solubilization through release of organic acids and still unknown mechanisms. Artificial acidification of the culture medium with HCI did not cause considerable P solubilization compared with our two isolates. In nonsterile soil both organisms caused a marked increase in the P fraction extracted with LiCl solution.