Leaching experiments of bone-meal phosphorus (P) solubilization by the sulfur-oxidizing bacteria Acidithiobacillus thiooxidans was carried out using the shake-flask methodology. The effects of bone meal dosage, bio-sulfur (bio-S) concentration, and amount of bacterial inoculum on the efficiency of P solubilization were determined. The bone meal was dissolved in bacterially produced sulfuric acid to form "soluble P." An increase in concentration of bio-S as an energy substrate for the acidophilic A. thiooxidans increased the P solubilization efficiency. Upon addition of 5% bio-S, 10% bone meal, and 10% A. thiooxidans to the leach suspension, its pH dropped from 5.22 to 1.92 between days 30 and 40 of the leaching experiment; this resulted in an increase in water-soluble P concentration by 23.8 g P 2 O 5 L -1 . The soluble P concentration in the suspension from the bioleaching experiment was >20 times higher than that in conventional liquid bone-meal fertilizers. Inorganic nutrients, such as N, Ca, and Mg, were also solubilized in the suspension during the bioleaching experiment. The role of bio-S as an energy substrate for acidophilic bacteria to leach P from bone meal during formulation of biofertilizers could potentially be exploited in the management of crop nutrients in organic farming.