岑溪药用野生稻高效内生固氮菌分离及促生特性

【目的】以广西岑溪市野生稻保护区的药用野生稻为材料，分离纯化内生细菌，筛选固氮酶活性较高和对作物促生效果较好的菌株。【方法】利用乙炔还原法检测固氮酶活性，采用SDS-PAGE全细胞蛋白电泳和IS-PCR指纹图谱技术对分离到的固氮菌进行聚类。利用16S rRNA基因和nifH基因确定其系统发育地位。采用钼锑抗比色法、Salkowski比色法和CAS检测法分别测定菌株溶磷性、生长素的分泌能力和产铁载体能力。通过平板和盆栽试验检测其对水稻的促生作用。【结果】共分离得到35株内生固氮菌，分为6个类群。其中CX24固氮酶活性最高，经鉴定属于Klebsiella variicola，其固氮酶活性为298.64 μmol/(L·h)，为参比模式菌株DSM15968的9倍。另外该菌株还具有较高的溶磷性、分泌生长素和产铁载体能力，能够有效地促进水稻的萌发和生长。【结论】菌株CX24属于Klebsiella variicola，是一株高效内生固氮菌，具有很好的生产应用前景。

Isolation and characterization of plant growth promotion of efficient endophytic diazotrophs from Oryza officinalis wall in Cenxi

Objective] To screen efficient nitrogen fixation and plant growth promoting endophytes from Oryza officinalis wall in Cenxi, Guangxi. Methods] The nitrogen-fixation ability of the isolates was tested by acetylene reduction assay. The SDS-PAGE patterns of the whole-cell protein electrophoresis and IS-PCR DNA finger-printings were used to group these isolates. Phylogenetic analysis based on 16S rRNA gene and nifH gene was performed. The ability of indole acetic acid secretion and the production of siderophore were tested by the Salkowski colorimetric method and the blue plate assay, separately, and the ability of phosphate solubilization also was detected. The property of plant growth promoting rice was tested by plate and potting. Results] A total of 35 endophytic diazotrophs were isolated and classified into 6 groups, in which CX24 belonging to the Klebsiella variicola showed the highest nitrogenase activity. The nitrogenase activity (298.64 nmol/(mL·h)) was 9 times as much as the reference strain DSM15968. Besides the secreting siderophore, indole acetic acid and ability of solubilize phosphorus, the strain CX24 could also effectively promote the germination and growth of rice. Conclusion] The strain CX24 belonging to Klebsiella variicola, was an efficient endophytic diazotroph and had a very good application prospect.