Abstract: Biological nitrogen fixation is the cleanest and the most economical nitrogen fertilizer because it can reduce the environmental pollution and save energy.Endophytic nitrogen-fixing bacteria,living in plants,can avoid being inhibited by nitrogen compounds and the competition with indigenous microorganisms,showing a higher efficiency of nitrogen fixation.Endophytic nitrogen-fixing bacteria have great potentials to settle the problem of nitrogen sources of the host plants and enhance the adaptability to the environment.Now,more than 20 genera endophytic nitrogen-fixing bacteria have been found from the economic crops and tropical plants,but few studies on the alpine grassland Polygonum viviparum endophytic nitrogen-fixing bacteria are reported.In this study,endogenous nitrogen-fixing bacteria were isolated,screened and identified from Polygonum viviparum which are advantageous plants in alpine grassland in the Eastern Qilian Mountains.14 endophytic bacteria were isolated from Polygonum viviparum,and 7 of them have the ability of nitrogen-fixing.Z22 has been logged in the Gene Bank and has an accession number of EU693342 after PCR amplification,sequencing and phylogenetic analysis on nitrogen-fixing genes(nifH) Z22.Z22 is spherical,Gram-positive,and produces spore.Both 16SrDNA sequence homology analysis and physiological biochemical characteristics analysis indicated that Z22 can be identified as Bacillus sphaericus.16SrDNA sequence of Z22 has got a Gene Bank accession number of EU236749.It is the first time that gene sequence of nifH of encoding ferritin of Bacillus sphaericus was gained.

Key words: Polygonum viviparum, endophytic bacteria, Bacillus sphaericus, nitrogen fixation gene(nifH)

摘要： 从东祁连山高寒草地采集优势植物珠芽蓼(Polygonum viviparum)并对其内生固氮细菌进行分离、筛选和鉴定。结果表明:从珠芽蓼内分离到14株内生细菌,其中Z22、Z24、Z25、Z27、Z28、Z211、Z214共7株内生细菌具有固氮能力,对菌株Z22的固氮基因(nifH)进行了PCR扩增、测序和系统发育分析,并在GenBank中登录(登录号为EU693342);Z22菌体球形,革兰氏阳性,产芽孢,结合生理生化特征及16SrDNA基因序列测定和同源性分析,鉴定其为球形芽孢杆菌(Bacillus sphaericus),该菌株的16SrDNA序列在GenBank中登录(登录号为EU236749)。本文首次获得了球形芽孢杆菌编码铁蛋白的nifH基因序列。

关键词: 珠芽蓼, 菌株, 球形芽孢杆菌, 固氮基因