西藏青稞根际细菌群落结构及多样性

Structure and diversity of the bacterial community in the rhizosphere of highland barley in Xizang

摘要:

【目的】分析西藏不同种植区青稞根际土壤细菌群落结构及其影响因素，揭示特定环境下根际细菌生物标志物，为发掘研究优异根际促生菌及其作用提供参考。【方法】采用16S rRNA基因高通量测序技术和数据统计分析，比较了西藏5个市青稞种植区根际土壤细菌群落组成和结构差异，分析了青稞根际细菌生物标志物及群落结构变化的驱动因素。【结果】通过测序45个根际土壤样品获得10 715个操作分类单元（operational taxonomic units，OTUs），共43门、1 244属、2 783种，其中放线菌门（Actinobacteriota）、变形菌门（Proteobacteria）、绿弯菌门（Chloroflexi）、酸杆菌门（Acidobacteriota）、拟杆菌门（Bacteroidota）、厚壁菌门（Firmicutes）、芽单胞菌门（Gemmatimonadota）、粘球菌门（Myxococcota）和髌骨细菌门（Patescibacteria）为优势菌门，相对丰度占比94.92%-96.56%。五个市的根际细菌群落结构存在明显的差异，组间差异大于组内差异（R=0.226 9，P=0.001），其中放线菌门、绿弯菌门、酸杆菌门、拟杆菌门和髌骨细菌门丰度存在显著性差异（P<0.05）。五个市青稞根际土壤存在潜在生物标志物，拉萨和山南只有3个和6个特有细菌进化支，共现网络更为复杂、OTUs间联系更为紧密。变形菌门、绿弯菌门、放线菌门和酸杆菌门是青稞根际土壤中主要的关键细菌门，内生菌门、Methylomirabilota和蓝细菌分别是林芝市、日喀则市和山南市的特有关键类群。青稞根际细菌群落结构的变化主要与环境因子pH、全钾（total potassium，TK）、速效钾（available potassium，AK）、碳磷比（C：P）和海拔有关，其中TK是影响根际土壤细菌群落最重要的因子（r²=0.621 4，P=0.001）。【结论】西藏青稞根际细菌多样性丰富，5市间存在显著差异，且不同生长区青稞根际具有特有的生物标志物，为进一步研究特有根际细菌在青稞生长和环境适应中的作用，发掘优异根际促生菌提供参考。

Abstract:

[Objective] This study aims to analyze the structure and influencing factors of bacterial community in the rhizosphere soil of highland barley in different planting areas in Xizang, reveal the biological markers of rhizosphere bacteria in specific environments, and provide a reference for the exploration and research of rhizosphere growth-promoting bacteria and their roles. [Methods] We carried out 16S rRNA gene high-throughput sequencing and statistical data analysis to compare the composition and structures of the bacterial communities in the rhizosphere soils of highland barley cultivated in five cities of Xizang. We then analyzed the biological markers and the driving factors of community structure changes in the rhizosphere bacteria of highland barley. [Results] The sequencing of 45 rhizosphere soil samples yielded 10 715 operational taxonomic units (OTUs), which belonged to 2 783 species, 1 244 genera of 43 phyla. Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota,Bacteroidota, Firmicutes, Gemmatimonadota, Myxococcota, and Patescibacteria were the dominant bacterial phyla, with the relative abundance of 94.92%-96.56%. The community structure of rhizosphere bacteria showed significant differences among the five cities, with greater inter-group differences than intra-group differences (R=0.226 9, P=0.001). Actinobacteriota, Chloroflexi, Acidobacteriota, Bacteroidota, and Patescibacteria showed different relative abundance among the five cities (P<0.05). We identified potential biological markers in the rhizosphere soil of barley in all five cities. There were potential biological markers in the rhizosphere soil of highland barley in the five cities. Lasa and Shannan had only three and six unique bacterial clades, respectively, with more complex co-occurrence network and tighter connections between OTUs. The key phyla in the rhizosphere of highland barley were Proteobacteria, Chloroflexi,Actinobacteriota, and Acidobacteriota. Additionally, Endobacteria,Methylomirabilota, and Cyanobacteria were unique taxa in Linzhi, Rikaze, and Shannan, respectively. The changes in the bacterial community structure in the rhizosphere of highland barley were mainly related to environmental factors such as pH, total potassium, available potassium, carbon to phosphorus ratio, and altitude, with total potassium being the most important factor (r²=0.621 4, P=0.001). [Conclusion] The bacteria in rhizosphere soil of highland barley in Xizang have high diversity, with significant differences among the five cities. Additionally, different growing areas of highland barley have unique biological markers of bacteria in the rhizosphere. The findings provide a reference for revealing the role of unique rhizosphere bacteria in the growth and environmental adaptation of highland barley and for exploring excellent rhizosphere plant-promoting bacteria.