New isolation method for microorganisms solubilizing iron and aluminum phosphates using dyes

Two pH indicator dyes, bromo cresol green (BCG) and bromo phenol blue (BPB) were used to develop a new method for the isolation of microorganisms that solubilize iron and aluminum phosphates based on the fact that the solubilization of iron and aluminum phosphates was associated with the decrease of the pH. BCG was found to be superior to BPB in terms of clarity and visibility. The use of Reyes's basal medium plus dye was found to be preferable to that of Pikovaskaya's medium plus dye in terms of halo zone formation. These results indicated that Reyes's basal medium plus BCG is the best medium for the isolation of iron and aluminum phosphates-solubilizing microorganisms. Four efficient iron phosphate solubilizers and five efficient aluminum phosphate solubilizers were isolated on Reyes's basal medium containing FePO4 and AIPO(4), respectively, plus BCG.