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为了充分挖掘土壤“磷库”资源,减少化学磷肥的施用量,减轻磷肥施用导致的农业面源污染问题,以PVK培养基为分离培养基从玉米根际土壤中分离到1株溶磷菌XS2,结合菌落形态特征、生理生化试验和16S rDNA方法对其进行分类鉴定;利用L25(53)正交设计试验,从碳源、氮源及pH对菌株XS2溶磷培养条件进行优化;利用优化后的PVK培养基测定了菌株XS2对多种难溶性磷源的溶解特点;采用高效液相色谱法分析了菌株XS2发酵液中有机酸的变化,对其溶磷机制进行初步分析.结果表明:溶磷菌株XS2为巨大芽孢杆菌(Bucillusmegaterium).正交试验结果表明:在以葡萄糖为碳源,硫酸铵为氮源,pH 5条件下溶磷量最高,为401.33 mg/L;菌株XS2对Ca3(PO4)2、A13(PO4)2、FePO4和磷矿粉均有较好的溶解能力;发酵液中含有草酸、苹果酸、柠檬酸、乳酸、乙酸、琥珀酸和几种未知酸,其中有机酸的种类和含量随培养时间的变化而不同,柠檬酸、乳酸、乙酸和草酸可能是影响菌株溶磷的重要有机酸,试验获得了1株溶解难溶性磷的巨大芽孢杆菌XS2,它能够将多种难溶性磷转化为植物可利用的有效磷,从而增加土壤中的有效磷含量,提高作物产量,为从源头上解决磷肥施用导致的农业面源污染问题提供材料.“,”In order to fully mobilize phosphorus resources of soil,reduce the application amount of chemical phosphorus fertilizer,and then reduce agricultural non-point source pollution caused by the application of phosphate fertilizer,one phosphate-solubilizing bacterium named XS2 was isolated from rhizosphere soil of maize by PVK medium and identified by colony morphology characteristics,physiological and biochemical tests and 16S rDNA sequence analysis.The phosphate-solubilizing conditions were optimized in 3 aspects of carbon source,nitrogen source and pH value by using L25(53) orthogonal tests,the dissolution characteristics of strain XS2 were determined for a variety of insoluble phosphate sources,the changes of organic acids in the fermentation broth of strain XS2 were analyzed by HPLC and the phosphate-dissolving mechanism was primarily analyzed.The results show that strain XS2 belonged to Bucillus megaterium,and the phosphate-solubilizing capacity reached the highest level of 401.33 mg/L under the conditions of glucose as carbon source,ammonium sulfate as nitrogen source and pH 5.The strain had better ability to dissolve Ca3(PO4)2,A13(PO4)2,FePO4 and phosphate powder.Oxalic acid,malic acid,citric acid,lactic acid,acetic acid,acetic anhydride and several unknown acids were determined by HPLC and the kinds and contents of organic acids in culture medium were different with the change of culture time.Citric acid,lactic acid,acetic acid and oxalic acid seemed to be the major organic acids which affect the dissolution of phosphorus.A strain of Bacillus megaterium XS2 was obtained and identified as P.decumbens.It can convert insoluble phosphorus into available phosphorus for plants,increasing content of effective phosphorus in soil and crop yield and providing data and theoretical basis for the solution of widespread pollution caused by the overuse of phosphate fertilizer from the source.