Abstract: Nitrogen-fixing Paenibacillus strains are considered as an excellent strain for microbial fertilizers because of its characteristics of nitrogen fixation, plant growth promotion, stress resistance and storage tolerance. However, the resources of identified strains are very limited. In this study, 60 nitrogen-fixing Paenibacillus strains with nifH genes were isolated from 500 strains which were isolated from the rhizospheres of 266 different plants in 20 provinces of China. The sequence of nifH genes and 16S rRNA from 17 isolations were analyzed. All of 17 isolations was preliminarily determined by constructing phylogenetic trees. The analysis of plant growth-promoting activities showed that all the 17 isolations had nitrogenase activity up to 2 109.9±131.1 nmol/mg·h, 5 isolations had IAA secretion ability up to 49.908±3.6 μg/mL, and 11 isolations had antagonism to 4 common plant pathogens. Among the 17 isolations, 5 had nitrogenase activity, IAA secretion and antagonistic action, among which BJ-18 with the lowest IAA secreting capacity still had significant growth promoting effect on tomato seedlings. This study provided a basis for enriching the resources of nitrogen-fixing microbial agents in China and even in the world, and provided high-quality experimental materials for the study of nitrogen-fixing mechanism.

Key words: Paenibacillus, nitrogenase activity, nif gene, IAA, antagonistic activity of plant pathogens

摘要： 固氮类芽孢杆菌是一类能产生芽孢、具有固氮能力的革兰氏阳性细菌。这类菌除固氮活性和抗逆力强外，有些菌株还具有促进植物生长、对植物病原菌有抑制作用、耐贮藏等特点，被认为是制备微生物肥料的优良菌种之一，但目前经过鉴定的菌种资源十分有限。从全国20个省不同地理环境、不同种类植物根际采集分离筛选获得500个菌株，从中鉴定出60个具有固氮结构基因（nifH）的分离株，通过对其中17个分离株的nifH和16S rRNA基因序列的比对分析，初步确定了它们的系统发育地位，17个分离株均属于固氮类芽孢杆菌，而且这17个菌株全部具有固氮酶活性，最高达到2 109.9±131.1 nmol/mg·h。进一步分析，其中5株具有IAA分泌能力，最高为49.908±3.6 μg/mL ，11株对4种常见植物病原菌表现出抑制作用。在17个分离株中，共发现了5株兼具固氮、分泌IAA以及抑制植物病原菌的特点，其中IAA分泌能力最低的BJ-18对番茄幼苗仍具有显著的促生作用。分离和鉴定的固氮类芽孢杆菌丰富了固氮微生物菌种资源，发现的兼具固氮、分泌IAA以及抑制植物病原菌的固氮类芽孢杆菌在农业生产中具有潜在的广泛应用前景。

关键词: 固氮类芽孢杆菌, 固氮酶活性, nif基因, 吲哚乙酸, 抑菌作用