Investigation of biological behavior and colonization ability of Iranian indigenous phosphate solubilizing bacteria

Soil phosphorous (P) uptake mechanisms by the interaction of plants and soil microorganisms benefit plant growth with preparing agriculture inoculants. But it is influenced by soil factors. The present study was performed to identify three effective strains of phosphate solubilizing bacteria (PSB) on the basis of 16S rDNA sequence in vitro. Bacillus lentus strain PS5, Bacillus licheniformis strain PS7 and Pseudomonas putida strain PS13 were isolated from an alkaline soil in Iran and the rhizosphere of Beta vulgaris and Solanum tuberosom. Their high root colonization ability and P solubilizing activity was detected in relation to soil physical and chemical properties influenced by environmental factors including salinity of 800 mM/L and temperature of 42 °C.Root colonization assays were performed to determine the distribution and metabolic activity of the bacterial isolates obtained from the potato rhizosphere. The seedling was planted in the soil sample inoculated with three strains after lux bioluminescence gene insertion and also marking for resistance to kanamycine and rifampin. Then it was placed in non-sterile natural soil. The introduced bacterial strains were quantified by dilution plating on antibiotic media together with observation of bioluminescence. The results demonstrated that these strains could survive in the potato root system at high temperature, high H+ concentrations and high salt concentrations. These three bacterial isolates possessed the ability to solubilize phosphate under stress conditions of alkaline soils in Iran as high salinity, high H+ concentrations and high temperature.