春兰根中可分泌吲哚乙酸的内生细菌多样性

Diversity of IAA-producing endophytic bacteria isolated from the roots of Cymbidium goeringii

植物内生细菌可通过分泌吲哚乙酸(Indole-3-aceticacid,IAA)等方式促进植物生长。本研究以温室盆栽春兰(Cymbidium goeringii)为材料,采用分离培养方法对春兰根中可分泌IAA的内生细菌多样性进行了研究。从春兰根组织中共分离纯化得到了256株内生细菌,其中57株具有分泌IAA的能力,占总菌数的22.3%。根据ARDRA(amplified ribosomal DNA restriction analysis)及16SrDNA系统发育分析结果,将57株内生细菌划分为25个组,分属于6大类群,分别为变形菌门的α-变形菌纲(35.1%)、γ-变形菌纲(14.0%)和β-变形菌纲(8.8%)、厚壁菌门(33.3%)、放线菌门(7.0%)及拟杆菌门(1.8%)。其中变形菌门的α-变形菌纲和厚壁菌门为优势类群,类芽孢杆菌属(Paenibacillus)为优势菌属,且为高产IAA的主体菌属。另外,测序结果显示有4个菌株的序列与已知细菌的最高序列相似性低于97.0%,可能为潜在的新种或新属。研究结果表明春兰根中分泌IAA的内生细菌具有丰富的多样性。这一结果可为研究和开发植物促生细菌提供基础资料。

Endophytic bacteria can directly stimulate plant growth in several ways, including production of plant hormones such as indole-3-acetic acid（IAA）.We investigated the diversity of IAA-producing endophytic bacteria in the roots of Cymbidium goeringii using culture-dependent approaches.A total of 57 IAA-producing strains were obtained from 256 strains isolated from the interior roots of C.goeringii.Based on amplified ribosomal DNA restriction analyses（ARDRA） and 16S rDNA sequences, these 57 strains were divided into 25 groups.The IAA-producing endophytic bacteria were grouped into six phyla, i.e., Alphaproteobacteria（35.1%）, Firmicutes（33.3%）, Gammaproteobacteria（14.0%）, Betaproteobacteria（8.8%）, Actinobacteria（7.0%） and Bacteroidetes（1.8%）.The dominant groups were Alphaproteobacteria and Firmicutes, and the dominant genus, Paenibacillus, produced relatively high levels of IAA.In addition, four potential novel taxonomic units were found.Our results revealed diverse and abundant communities of IAA-producing endophytic bacteria in the roots of C.goeringii and highlight the microbial resources represented by plant growth-promoting bacteria.