ISOLATION AND BIOCHEMICAL CHARACTERIZATION OF PHOSPHATE SOLUBILIZING MICROBES

Abstract

Phosphorus (P) is one of the essential macronutrients for plant growth and reproduction. Plants acquire P from the soil solution as phosphate anions. However, phosphate anions are extremely reactive and may be immobilized through precipitation with cations such as Ca2+, Mg2+, Fe3+ and Al3+, depending on the particular properties of the soil and as a result, the phosphate is highly insoluble and unavailable to plants. Application of phosphate-solubilizing fungi (PSF) has been added as fertilizer to increase P uptake and plant growth. The improvement of soil fertility is one of the most common strategies to increase agricultural production. Maintaining high levels of available nitrogen (N) and phosphorus (P), the two most limiting nutrients in soil, remains being a challenge. Major researches on biofertilizer have concentrated on understanding and improving N2 fixation. However, it is known that every aspect of the process of nodule formation is limited by the availability of P. Legumes like alfalfa and clover show a high positive response to P supplementation (Gyaneshwar et al., 2002), but most of the supplemented P become unavailable when its reacts with soil components. Many soil microorganisms are able to solubilize this unavailable P through their metabolic activities exudating organic acids, which directly dissolve the rock phosphate, or chelating calcium ions that release P to the solution. Production of microbial metabolites results in a decrease in soil pH, which probably plays an important role in the solubilization (Abd-Alla, 1994). Phosphate solubilizing bacteria (PSB) were isolated from the area around Bidar region and screened on the basis of their solubilization of inorganic tricalcium phosphate in liquid cultures. Ten strains that had higher solubilization potential were selected, and they characterized.