西藏色季拉山垂直植被带土壤细菌群落组成及功能潜势

Soil bacterial community composition and functional potentials along the vertical vegetation transect on Mount Segrila,Tibet,China

研究青藏高原土壤微生物群落组成和功能的空间分布特征有助于深入理解典型高寒生态系统中土壤微生物的重要生态功能。本研究采用16S rDNA高通量测序方法,分析了西藏色季拉山4个不同海拔土壤细菌群落物种组成和功能潜势的变化特征及其驱动因子。结果表明:随着海拔的升高,土壤细菌的丰富度和Shannon多样性指数显著降低;酸杆菌门、绿弯菌门、芽单胞菌门和硝化螺旋菌门的相对丰度显著增加,而变形菌门、放线菌门和拟杆菌门的相对丰度则显著降低。KEGG二级代谢通路中,膜运输及氨基酸、脂类、萜类和聚酮类化合物代谢相关基因的相对丰度在高海拔显著降低,而碳水化合物代谢、信号转导、复制与修复、酶家族等基因丰度则显著升高。不同海拔土壤细菌群落组成和功能潜势的变化受到植被和土壤因子的显著影响,并且pH值是关键驱动因子。群落功能潜势与放线菌门、拟杆菌门、纤维杆菌门等种群丰度显著相关。不同海拔下群落KEGG代谢通路基因组成的差异(β多样性)与土壤细菌群落结构的差异呈显著正相关,说明微生物群落组成与功能潜势之间可能存在紧密关联。

Information on the spatial distribution of soil microbial communities on the Tibetan Pla-teau is critical for in-depth understanding the important roles of microbes in typical alpine ecosystems.In this study,16 S rDNA Illumina Miseq sequencing was used to analyze the variations in bacterial community composition and functional potentials in soils sampled from four elevations on Mount Segrila,Tibet,and the driving environmental factors.Results showed that richness and Shannon diversity index of soil bacteria significantly decreased with increasing altitude.The relative abundances of Acidobacteria,Chloroflexi,Gemmatimonadetes,and Nitrospirae significantly increased,whereas that of Proteobacteria,Actinobacteria and Bacteroidetes significantly decreased with increasing altitude.In KEGG pathway(levelⅡ),the relative abundance of genes related to membrane transport and the metabolism of amino acids,lipids,terpenoids and polyketones was significantly lower at high elevations.In contrast,genes related to carbohydrates metabolism,signal transduction,replication and repair and enzyme family were more abundant at high altitudes.Soil bacterial community composition and predicted functions were significantly affected by vegetation types and soil properties,with soil pH being the key driver.There were significant correlations between the abundances of predicted functions and bacterial taxa,such as Acitnobacteria,Bacteroidetes,and Fibrobacteres.The dissimilarity in the composition of KEGG pathway genes along the elevational gradient(β-diversity)showed a significantly positive correlation with the dissimilarity in bacterial community structure,indicating that there was a strong relationship between microbial community composition and potential functionality.