ISOLATION OF PHOSPHATE SOLUBILIZING BACTERIA FROM SOIL AND IDENTIFYING PRODUCED ORGANIC ACIDS

Abstract

Phosphate solubilizing bacteria (PSB) were isolated from agricultural soil samples using pikovskayas medium. The Isolates were purified and identified based on morphology and biochemicals tests. Results showed two isolates namely , Pseudomonas spp. (P) and Bacillus spp. (B) reported as phosphate solubilizing bacteria . Their activity to solubilize tricalcium phosphate in broth cultures was examind.P-solubilizing action of these PSB was associated with the released organic acids and drop in pH of the cultures.Spectrophotometer was used to quantify phosphate solubilization in broth cultures at 430 nm.The isolate P3 was superior in solubilized phosphate (317.5 mgl-1) whereas lowest amount of solubilized phosphate (30.9 mgl-1)coincided with decreased pH of mediums of difference isolates. P3 isolate produced many organic acids ,therfore pH was decreased to 4.80 compared with 6.80 in control and B1 6.60.The results showed a negative relationship between pH and P-solubilized .High performance liquid chromatography analysis detected five different kinds organic acids namely : citric acid , gluconic acid , lactic acid , propionic acid and succinic acid in the cultures. It was concluded that bacteria was involved in arange of processes that affect the transformation of soil P .Phosphate solubilizing bacteria has attracted the attention of agriculturists as soil inoculums to improve the plant growth and yield,by solubilizing soil phosphate.