中文摘要：

通过组织表面消毒、切面培养和共生培养的方法从健康的穗花狐尾藻植株体内分离获得了一株具有较强溶磷能力的内生菌．系统发育分析和VITEK2系统鉴定结果表明，内生菌与沙雷氏菌的亲缘关系最近，因此，命名为Serratiasp．SP5．纯培养实验表明．菌株SP5通过产生酸性物质溶磷，在培养96h后溶磷能力达到最大，溶解性磷酸根的浓度高达269．60mg·L^-1，培养液的pH值下降至4．32．氮源通过降低菌株SP5的产酸能力而间接影响了其对磷的释放能力，菌株SP5溶磷的氮源优先利用顺序为铵根离子〉硝酸根离子〉尿素．适宜菌株SP5生长的pH值范围为5～9，酸性条件下菌株的溶磷能力大于碱性条件，而在pH值为7时与对照相比菌株对磷的相对释放量最大．pH值达到9时，菌株无明显溶磷能力．共存高浓度的金属离子时菌株SP5的溶磷效果明显降低，影响程度的大小顺序为Mn〉Fe〉Mg．菌株SP5溶磷的最佳碳氮比为35：1．在相同碳氮比下，不同的碳氮量会明显影响溶磷效果．底泥模拟培养条件下，菌株SP5可通过释放底泥中的闭蓄态磷（O-P）和钙磷（Ca-P）而明显提高水相中的磷酸根离子浓度，与对照相比，底泥中这两种磷形态分别下降了15．21％和34．87％，而水相中溶解性磷酸根离子是对照的1．5-2．0倍．研究结果为研究富营养化水体中磷的生物地球化学过程提供了新的科学数据．

英文摘要：

An endophytic bacterium with strung ability to dissolve phosphate was isolated from healthy Myriophyllumby spicatum by the methods of tissue surface disinfection, section culture and co-culture. According to the results of phylogenetic analysis and identification with VITEK 2 system, the endophytic bacterium shows high similarity with Serratia and was named Serratia sp. SPS. Strain SP5 dissolved phosphate through producing acidic substance with the highest soluble phosphate concentration of 269.60 mg.L-1 and pH of 4.32 after 96 h of cultivation. Nitrogen source indirectly affected the solubilization of phosphate, through decreasing the ability of strain SP5 to produce acidic substances. Results show that strain SP5 dissolved phosphate based on three types of nitrogen sources in the order of ammonium sulfate〉sodium nitrate〉urea. The satisfactory growth of strain SP5 was observed at pH 7-9. Strain SP5 dissolved more phosphate in acidic condition than in alkaline condition with the strongest relative phosphate dissolution ability at pH 7, but none at pH 9. The existence of metal ions decreased the solubilization of phosphate by strain SP5, in the order of Mn〉Fe〉Mg. The best ratio of C to N for strain SP5 to dissolve phosphate was 35：1. Under the same ratio of C to N, the content of carbon and nitrogen significantly affected the phosphate solubilization. Strain SP5 significantly increased the phosphate concentration in aqueous phase through releasing O-P and Ca-P in sediment. Compared with the control, the concentration of O-P and Ca-P in sediment decreased 15.21% and 34.87%, and the soluble phosphate concentration was 1.5-2 times higher than that of control. Results of this research provide new scientific data for the study of the biogeochemical processes of phosphorus in eutrophic water.