Which one of the following increases phosphate solubility

PSM i.e. Phosphate solubilizing microbes are a group of beneficial microbes present in organic matter of soil that makes insoluble phosphate available to plants by mineralization process, they make it soluble which is then easily absorbed and assimilated by plants. Pseudomonas aeruginosa was reported first time as a promising phosphate solubilizer and biofertilizer.