Sulfur Oxidizing Bacteria from Sulfur Rich Ecologies Exhibit High Capability of Phosphorous Solubilization

Sulfur oxidizing bacteria (SOB) oxidize elemental sulfur (S) and reduced S compounds to generate sulfuric acid which has the ability to solubilize and convert the insoluble phosphorous (P) compounds to simple plant available P compounds. In this study SOB strains were isolated from the samples collected from ten different ecologies and then screened on the basis of pH reduction (in thiosulphate broth media) and phosphorous solubilization index (PSI). Phosphorous solubilization efficiency of the ten selected SOB was tested in 0.5% tricalcium phosphate (TCP) broth media. Results indicated that the strain IW16 released 954.2 mg L-1 P (95.2%) during 32 days of incubation. Quantity of P dissolved had a significant positive correlation with the concentration of biologically produced sulfates by SOB (r = 0.80 0.89 0.91 and 0.92 after 8 16 24 and 32 days respectively). The most efficient SOB belonged to the sulfur rich ecologies such as industrial wastewater sewerage water and sulfur mud due to the availability of reduced S compounds in large quantities in these ecologies. Existence of SOB isolates in paddy wheat sugarcane and maize rhizosphere was due to the presence of reduced S compounds in the soil. The selected SOB were characterized for different morphological physiological and biochemical properties and were identified as the genus Thiobacillus. Copyright 2014 Friends Science Publishers