西北黄土高原柠条种植区土壤微生物多样性分析

Soil microbial diversity of artificial peashrub plantation on North Loess Plateau of China

摘要:

柠条锦鸡儿(Caragana korshinskii)是我国黄土高原区重要的饲用豆科灌木植物。为揭示土壤微生物与柠条种植之间的关系,采用未培养技术提取样品宏基因组DNA,分别构建柠条根表、根际和自然土16SrDNA文库,分析各文库微生物群落的变化。结果显示,随距离柠条根部渐远,微生物数量呈现递减趋势。聚类分析发现,变形杆菌纲是根表土壤区系中的优势微生物种群(70.3%),尤其存在大量α-Proteobacteria类的能诱使植物形成根瘤的根瘤菌和对植物有促生作用的γ-Proteobacteria类微生物;而在根际和自然土中,酸杆菌属(Acidobacteria)和古菌(Archaea)数量较多。柠条根际的多样性指数最高,而根表和自然土微生物类群具有较高的优势度,表现出从根表、根际植物相关微生物到自然土单一简单微生物类群的过渡。说明植物根系和土壤环境与微生物类群具有相互选择性。

Abstract:

Peashrub (Caragana korshinskii Kom) is a kind of excellent shrub used for dune-fixation in Loess Plateau of China. In order to explore relationship between peashrub and soil microorganisms，microbial communities diversity associated with rhizoplane，rhizosphere and bulk soil of peashrub in Loess Plateau of China were characterized based on a culture-independent approach. Three 16S rDNA gene libraries were constructed，respectively，and each different profile was used to define an operational taxonomic unit (OTU). The numbers of microorganisms decreased as root proximity decreased and a few OTUs became dominant. Phylogenetic analyses indicated that Proteobacteria was the predominant group in rhizoplane，which included many α-Proteobacteria，partially consisted of rhizobia，and γ-Proteobacteria beneficial to plant growth. In bulk soil，the most frequent OTUs were closely related to Archaea，while Acidobacteria was the dominant group in rhizosphere of peashrub. The diversity index (H′) was higher in rhizosphere than in rhizoplane and bulk soil，whereas microbial populations in rhizoplane and bulk soil had the greater dominance indices (D). It was shown that there was a significant change in microbial species composition along the root gradient，shifting from complex plant-associated bacterial community in the root habitats to a simple bacterial community in the bulk soil. These results showed that plant roots and soil conditions created a selective environment for microbial populations.