Isolation and Phosphate-Solubilizing Characteristics of PSM, Aeromonas hydrophila DA33

bacterium having high abilities to solubilize in-organic phosphate was isolated from cultivated soils. The strain was identified as Aeromonas hydrophila DA33, based on the physiological and biochemical properties. The optimum temperature and initial pH to solubilize insoluble phosphate in sucrose minimal medium were 3$0^{\circ}C$ and pH 5.0, respectively. In these conditions, phosphate-solubilizing activities of the strain against two types of insoluble phosphate were quantitatively determined. When glucose was used for carborn source, the strain had a marked mineral phospahte solubilizing activity. Inorganic phospahte solubilization was directly related to the pH drop by the strain. Analysis of the culture medium confirmed the production of gluconic acid as the main organic acid released by Aeromonas hydrophila DA33.