Screening and identification of phosphate-solubilizing bacteria from reclaimed soil in Shanxi mining area

【Objectives】The reclaimed soils are infertile and lack of available phosphate. Phosphate solubilizing bacteria are capable of transfering insoluble organic phosphorus and inorganic phosphorus into the available form for the utilization of plants. With the purpose of ecologicalyrecover the reclaimed soils, phosphorus solubilizing bacteria strains were screened and investigated for microbial fertilizer production.【Methods】Strains which had D/d value 1.5 were pre-screened using plate screening methods, then the strainsdisplaying phosphorus solubilizing efficiencyhigher than Bacillus megaterium As1.223 were picked out with hydroponics.The phosphate solubilizing ability and phosphatase activity of the isolated strainswere assessed in liquid culture with solubilizing rockphosphate and lecithin as P sources. The growth ability of strains assessed through their resistance to temperature, salt and pH variations. Strains were identified by the methods of morphology, gene sequencing and cellular fatty acid compositions analysis, colony morphology was observed on nutrient agar, microbial morphology was observed by scanning electron microscope, gene sequencing was performed by 16S rDNA sequence analysis and aligned in EzTaxon, and cellular fatty acid compositions analysis was carried out by the Sherlock Microbial Identification System (MIDI).【Results】About nineteen phosphorus solubilizing bacteria strains are screened from the reclaimed soils in Shanxi mining area with inorganic and organic phosphorus plate medium. The D/d values of seven strains are 1.5.In medium using Ca3(PO4)2 as the phosphorus source, the phosphorus solubilizing efficiencies of four strainsare higher than that of Bacillus megaterium As1.223, and the efficiencies are about 7.89%-12.61%. Among thefour strains, Y14 has the highest efficiency.In the medium containing lecithin, the phosphorus solubilizing efficiency and acid phosphatase activity of four strains are about 1.79%-3.07% and 24.3-28.4 U/L respectively, higher than those of As1.223. The alkaline phosphatase activities are about 11.9-50.2 U/L. Strain Y14 displays the highest phosphate-dissolving ability and phosphatase activity. The four strains also have strong environmental adaptability, and the performance of Y14 is the best. The Strains H22, Y11, and Y34 display 99% nucleotide homology with Pseudomonas sp., and the strain Y14 displays 99.79% with Pantoea sp. The cellular fatty acid compositions of the strains H22, Y11, and Y34 are similar with Pseudomonas sp., and the strain Y14 is similar with Pantoea sp. The strain H22, Y11, and Y34 are identified as Pseudomonas sp., while the strain Y14 is identified as Pantoea sp.【Conclusions】Four strainsare screened and identifiedhaving high phosphorus solubilizing capacity. The four strains belong to Pseudomonas sp. and Pantoea sp. respectively. The D/d values of the strain Y14 in inorganic and organic phosphorus plate medium are 3.28 and 1.59 respectively, the phosphorus solubilizing efficiencies in medium containing Ca3(PO4)2, rock phosphate, and lecithin are 12.61%, 1.21%, and 3.07% respectively, the acid and alkaline phosphatase activities are 28.4 U/L and 50.2 U/L respectively. The growth temperature for Y14 is from 20℃ to 60℃, pH 4 to 11 and NaCl 2% to 7%. Y14 is identified as Pantoea sp.According to the results of D/d value, phosphorus solubilizing efficiency, phosphatase activity and growth experiment, the strain Y14 is supposed to be the most suitable for popularizing in reclamation-area of Shanxi.