三倍体毛白杨不同组织内生细菌多样性分析

Diversity of endophytic bacteria in different tissues of triploid Populus tomentosa

摘要:

【背景】三倍体毛白杨非常适合黄河区域生态经济发展，是我国林业推广项目的重要树种。内生细菌在三倍体毛白杨不同组织中广泛存在，对三倍体毛白杨具有防病、促生、固氮和生物修复等生物学作用。【目的】通过分析三倍体毛白杨不同组织内生细菌多样性，可以充分挖掘其蕴含的丰富微生物资源。【方法】以北京林业大学山东冠县毛白杨基地的三倍体毛白杨为材料，应用16S rRNA基因高通量测序技术对其根、茎、叶中内生细菌多样性进行了分析，阐述三倍体毛白杨不同组织内生细菌多样性的变化趋势和规律，为其内生细菌的进一步应用奠定理论基础。【结果】三倍体毛白杨根部内生细菌群落丰富度及多样性最高，叶片中最低。高通量测序结果显示，在全部样本中，假单胞菌门和放线菌门为优势门，伯克氏菌属(Burkholderia)、假诺卡氏菌属(Pseudonocardia)和食酸菌属(Acidovorax)为优势属，不同组织的内生细菌群落结构组成差异显著；16S rRNA基因功能预测结果显示，三倍体毛白杨内生细菌的功能主要涉及氨基酸代谢、维生素代谢、芳香族化合物降解和糖酵解等。通过分离培养共获得217株内生细菌，分属于23个属44个种，其中有4株16S rRNA基因序列相似性低于97.5%的菌株，有可能为潜在的新种分类单元。【结论】三倍体毛白杨根茎叶内生细菌具有丰富的多样性，组间差异显著，内生细菌多样性和丰富度均是根>茎>叶。通过传统的分离培养方法获得了一些内生细菌资源，其中包含4株16S rRNA基因序列相似性低于97.5%的菌株。然而高通量测序结果显示，还有大量的内生细菌在此次实验中并未培养出来，需要进一步开发新的高通量分离培养和鉴定方法以充分挖掘更多未培养、难培养的内生细菌菌株。

Abstract:

[Background] Triploid Populus tomentosa is suitable for the ecological and economic development of the Yellow River and serves as an important tree species for forestry extension projects in China. Endophytic bacteria of triploid P. tomentosa play a role in the disease prevention, growth promotion, nitrogen fixation, and biological repair. [Objective] The objective was to analyze the diversity of endophytic bacteria and fully explore the microbial resources in triploid P. tomentosa. [Methods] In this study, the diversity of endophytic bacterial community in the roots, stems and leaves of P. tomentosa from the research base of Beijing Forestry University in Guanxian county, Shandong province was analyzed via 16S rRNA gene high-throughput sequencing and plate streaking. The variation trends and rules of endophytic bacterial diversity in different tissues of triploid P. tomentosa were clarified to lay a theoretical foundation for the further application of endophytic bacteria. [Results] The endophytic bacteria of triploid P. tomentosa had the highest richness and diversity in the roots while the lowest in the leaves. Pseudomonas and Actinobacteria were the dominant phyla, and Burkholderia, Pseudonocardia, and Acidovorax were the dominant genera. The structure of endophytic bacterial community varied among different tissues. The functions of the endophytic bacteria mainly involved amino acid metabolism, vitamin metabolism, degradation of aromatic compounds, and glycolysis. A total of 217 endophytic bacterial strains were isolated, belonging to 44 species of 23 genera. Among them, four strains shared the 16S rRNA gene sequence similarity below 97.5%, which might be new taxa. [Conclusion] In conclusion, the diversity of endophytic bacteria in the roots, stems and leaves of triploid P. tomentosa was significant. The diversity and richness of endophytic bacteria were higher in the roots than in the stems than in the leaves. Some endophytic bacterial resources were obtained by traditional isolation and culture methods, including 4 strains with 16S rRNA gene sequence similarity less than 97.5%. However, the results of high-throughput sequencing showed that a large number of endophytic bacterial strains had not been cultured in this experiment. It was necessary to further develop new high-throughput isolation, culture and identification methods to fully explore more uncultured and difficult endophytic bacterial strains.