青藏高原极端生境细菌多样性差异及影响因素

Differences and influencing factors of bacterial composition and diversity in seven typical extreme habitats on the Qinghai-Tibetan Plateau

摘要:

土壤微生物组对于生态系统的可持续性至关重要，青藏高原独特的地理环境孕育了多样的极端环境，其土壤细菌组成差异及其驱动因素尚不清楚。【目的】探究不同极端生境土壤细菌多样性及其影响因素。【方法】对7种典型的青藏高原极端生境土壤DNA进行16S rRNA基因高通量测序，通过生物信息分析，找出不同生境细菌群落组成、功能差异；结合土壤理化因子，进一步分析细菌组成差异的潜在影响因素。【结果】通过高通量测序，从7个不同生境的36个土壤样品中共获得16 323 712高质量reads，26 504个可操作分类单元(operational taxonomic units, OTUs)。在门分类水平上，各生境中注释到的放线菌门(Actinomycetota)与假单胞菌门(Pseudomonadota)相对丰度均最高；在属分类水平上，芽孢杆菌属(Bacillus)、Ambiguous_taxa、土壤红杆菌属(Solirubrobacter)、假节杆菌属(Pseudarthrobacter)等为优势属。另外，不同生境中的细菌α多样性无显著差异，但是β多样性差异显著，并且通过LEfSe分析进一步说明了不同生境细菌群落结构的差异性。通过冗余分析(redundancy analysis, RDA)发现，Mg²⁺、Na⁺和K⁺等常量元素是影响细菌群落结构的主要因子，而且其他土壤理化因子对不同生境中优势菌群的分布具有一定的特异性。最后，利用FAPROTAX工具对细菌群落功能预测，发现不同生境的细菌类群参与的氮、硫元素生物地球化学循环过程差异较大。【结论】青藏高原不同极端生境细菌群落结构差异较大，这一成因受到不同土壤理化因子的驱动，并且各生境下大量未注释菌属表明青藏高原具有极为丰富的潜在细菌新物种资源。

Abstract:

Soil microorganisms play a key role in the sustainability of ecosystems. There are diverse extreme habitats on the Qinghai-Tibetan Plateau (QTP), where the differences of soil bacterial composition and the driving factors remain to be studied. [Objective] To explore the differences and influencing factors of soil bacterial diversity in different extreme habitats on the QTP. [Methods] High-throughput sequencing of 16S rRNA genes was performed for the soil samples from seven typical extreme habitats on the QTP. The bioinformatics tools were employed to analyze the differences in bacterial composition and functions among different habitats. The potential soil factors influencing bacterial composition were further analyzed. [Results] A total of 16 323 712 high-quality reads and 26 504 operational taxonomic units (OTUs) were obtained for the 36 soil samples collected from seven different habitats. At the phylum level, the relative abundance of Actinomycetota and Proteobacteria were the highest in all the habitats. Bacillus, Ambiguous_taxa, Solirubacter, and Pseudoarthrobacter were the dominant genera. In addition, there was no significant difference in bacterial alpha diversity among different habitats, while the bacterial beta diversity showed significant differences, which was further confirmed by Linear discriminant analysis Effect Size (LEfSe). Redundancy analysis (RDA) identified Mg²⁺, Na⁺, and K⁺ as the main factors affecting the bacterial community structure, and the effects of other soil physicochemical factors on the distribution of dominant flora varied in different habitats. Finally, FAPROTAX tool was used to predict the bacterial function, which suggested that the roles of bacteria in the biogeochemical cycling processes of nitrogen and sulfur varied in different habitats. [Conclusion] The bacterial community structure varies greatly in different extreme habitats of the QTP, which is driven by different soil physicochemical factors. The presence of rich unannotated genera in each habitat indicates that the QTP has rich potential new bacterial resources.