大豆根际溶磷菌分离鉴定及溶磷过程中有机酸的分泌

【目的】明确吉林省地区大豆Glycine max根际溶磷菌的种类及溶磷特点。【方法】利用溶磷圈法筛选溶磷菌,16S rDNA序列测定和Vitek2生理生化系统对菌株进行分析鉴定。测定菌株生长量、溶磷量、培养基pH变化与有机酸的产生。【结果】从大豆根际土壤中分离获得4株溶磷菌株WJ1、WJ3、WJ5和WJ6。4个菌株分别属于假单胞菌属Pseudomonas sp.、肠杆菌属Enterobacter sp.、苍白杆菌属Ochrobacterum sp.和克雷伯菌属Klebsiella sp.。4株溶磷菌96 h内最大溶磷量分别为558、478、596和586μg·m L-1。甲基红试验和培养物p H测定结果表明:4个菌株在溶磷过程中可使培养物的pH下降,当p H小于4时,会明显阻碍菌株的生长。p H为5时,WJ1和WJ3的生长受到轻微的影响,WJ5和WJ6能正常生长。GC-MS对菌株在溶磷过程中产生的有机化合物的分析表明,4菌株均分泌多种有机酸,其中α-酮戊二酸在WJ1、WJ3和WJ6菌株溶磷过程中大量产生。【结论】4菌株具有较好的溶磷能力,溶磷过程中分泌有机酸种类不完全相同,有机酸的分泌造成培养基的p H降低,影响菌体生长,而菌体数量决定各菌株的溶磷量。

Identification of PSB in soybean rhizosphere and secretion of organic acids in the process of phosphate solubilizing

Objective] In order to determine the species and characteristics of phosphate solubilizing bac-teria ( PSB) in soybean, Glycine max, rhizosphere soil in Jilin Province.Method]PSB were screened based on the formation of a halo zone of dissolving phosphate, and were identified by 16S rDNA gene sequencing and Vitek 2 system. Bacterial growth rates, soluble phosphorus concentrations, pH changes of the media and the types and amounts of secreted organic acids were determined. Result]WJ1, WJ3, WJ5 and WJ6 were isolated from soybean rhizosphere soil, and were identified as Pseudomonas sp. , Enterobacter sp. , Ochrobacterum sp. and Klebsiella sp. respectively. The maximum soluble phosphorus concentrations within 96 h of inoculating four PSB were 558, 478, 596 and 586 μg·mL-1 respectively. The methyl red tests and pH measurements indicated that media pH all decreased during the phosphate solubilizing process of four PSB. Bacterial growth was limited when pH was below 4. Growth of WJ1 and WJ3 were slightly affected at pH 5, whereas WJ5 and WJ6 grew normally. Various organic compounds secreted from four PSB were analyzed by GC-MS, and among them α-ketoglutaric acid was identified as an abundant compound secreted by WJ1 , WJ3 and WJ6 .Conclusion]All four PSB can effectively solu-bilize phosphate. The types of organic acids produced by the four PSB are not exactly the same,and the secretion of organic acids causes medium pH to decline, which inhibit the bacterial growth. The number of the bacteria determinines the amount of dissolved phosphorus.