Phosphate-solubilizing potentiality of the microorganisms capable of utilizing aluminium phosphate as a sole phosphate source.

Eight bacteria, each of the genus Bacillus, two actinomycetes, each of the genus Streptomyces, and six fungi, one each of the genus Penicillium and Chaetomium and four of the genus Aspergillus, were isolated on AlPO4-sucrose agar from a typical Indian lateritic soil (Typic Ochragualf). All of them were capable of solubilizing Ca3(PO4)2 to a higher degree than AlPO4. Bacillus subtilis (B-7655), LAB4, Bacillus sp., LAB5, Penicillium sp., LAF2, and Aspergillus spp., LAF3 and LAF4, were solubilizing Ca3(PO4)2 very efficiently, but AlPO4 to a lesser degree. Bacillus spp., LAB1, LAB2, LAB5, LAB6 and LAB7, Chaetomium nigricolor, LAF1, and Aspergillus spp., LAF5 and LAF6, were unable to bring detectable amounts of soluble phosphorus to solution from AlPO4. Except Chaetomium, all the other organisms produced free aliphatic organic acid in detectable amounts. The organic acids produced were oxalic, succinic, citric, and 2-keto gluconic acid. 2-Keto gluconic acid, singly and in combination with succinic or citric acid, accounted for higher solubilization. Amount of free organic acids in the growth medium was not directly correlated with phosphate solubilization.