Isolation and identification of a phosphate solubilizing bacterium Leuconostoc mesenteroides and its ability to dissolve phosphorus

Abstract:

[Background] Many microorganisms from plant rhizosphere soil have phosphate solubilizing ability, while phosphate solubilizing Leuconostoc mesenteroides have not been reported. [Objective] To isolate and identify efficient phosphate solubilizing bacteria from navel orange rhizosphere soil and investigate the application in phosphorus release. [Methods] Transparent circle assay was used to preliminarily screen the phosphate solubilizing bacteria. After secondary screening, soluble-P in the culture medium was determined by molybdate blue colorimetric method. Different parameters were determined to explore the phosphate solubilizing mechanism of one strain. The phosphate solubilizing mechanism of the strain was explored by measuring the content of low-molecular-weight organic acids in the fermentation broth, the enzyme activity of phosphatase and its pH value. [Results] Nine phosphate solubilizing strains out of 23 candidates were obtained after two step selection. Based on 16S rRNA gene sequence analysis and physiological and biochemical chanterization, a strain was obtained and named Leuconostoc mesenteroides G7. The optimal phosphate solubilizing conditions of the strain G7 were as follows: the initial pH was 6.0, the carbon source was glucose, and the nitrogen source was ammonium sulfate. G7 produced a mass of organic acids, and its acid phosphatase activity was higher than that of alkaline phosphatase. [Conclusion] Carbon source, nitrogen source and initial pH can influence the phosphate solubilizing ability of the strain G7. The phosphate solubilizing ability of G7 is mainly due to its large number of low-molecule organic acids produced during fermentation. The mechanism of phosphate solubilizing ability need to be researched thoroughly.