烟草根际固氮菌的筛选、鉴定及优化培养

Screening, identification and culture optimization of nitrogen-fixing bacteria in tobacco rhizosphere

对四川广元烟草主产区三个种植基地的烟草根际固氮菌进行筛选,分离出28株具有固氮活性的菌株。经扩增r DNA限制性酶切片段分析法(ARDRA)初步分类,共获得5个操作分类单元(OTU),并由16S rDNA序列进行了分析鉴定。结果表明不同分类单元分别是:苏云金芽孢杆菌、枯草芽孢杆菌、甲基营养型芽孢杆菌、巨大芽孢杆菌和炭疽杆菌。优化了N7菌株(巨大芽孢杆菌)培养条件,确定其最佳碳源为蔗糖,最适宜初始pH值为7.5,最适温度为30℃。

Twenty eight diazotrophs were isolated from rhizosphere soil samples from Guangyuan tobacco growing area, Sichuan province. These diazotrophs were isolated by using free nitrogen medium. Amplified r DNA restriction analysis（ARDRA）showed that all strains isolated could be classified into 5 Operational Taxonomic Units（OUT）. Different OUTs was identified by 16 S r DNA sequencing, and those were identified as Bacillus： Bacillus thuringiensis; Bacillus subtilis; Bacillus methylotrophicus; Bacillus megaterium and Bacillus anthracis. The batch culture conditions of isolate N7（Bacillus megaterium） were optimized via adjusting carbon sources, temperature and p H values. It was found that sucrose is the best carbon source, and the best initial p H value is 7.5, and the best temperature is 30℃.