Studies on mineral phosphate solubilization by cyanobacteria Westiellopsis and Anabaena

Two diazotrophic cyanobacteria, Westiellopsis prolifica and Anabaena variabilis were evaluated for elucidating the possible mechanism of mineral phosphate solubilization. Phosphate starved cyanobacteria evaluated for the presence of organic acids, extracellular compounds or enzymes that might have been produced and promoted the mineral phosphate solubilization with Mussorie Rock Phosphate and Tricalcium Phosphate as substrates. Both the cultures did not reveal production of organic acids throughout the incubation period when checked for decrease in media pH of the media and thin layer chromatography. Thin layer chromatography of culture filtrates showed the presence of hydrocarbon like compound. Further analysis of the culture filtrates with gas liquid chromatography, a single peak near to the retention time of 7.6 was observed in all extracts of culture filtrates irrespective of phosphate source. UV-visible spectra of culture filtrates revealed the absorption maxima of 276 nm. Gas chromatographic-mass spectrometric analysis of culture filtrates showed most intense peak in the electron impact (EI) ionization was at m/z 149 and molecular ion peaks at m/z 207 and 167, inferring the presence of phthalic acid. Among the mechanisms in mineral phosphate solubilization, it was evident that these cyanobacteria used phthalic acid as possible mode of P solubilization.