野葛根际固氮微生物群落分布特征及其影响因素

Distribution pattern and influencing factors of nitrogen-fixing microbial community in the rhizosphere of Pueraria lobata

摘要:

【目的】研究野葛根际固氮微生物群落的空间分布特征，同时结合地理气候因子、土壤理化性质探讨影响野葛根际固氮微生物群落的空间分布特征的主要因素。【方法】在野葛广泛分布的广西、江西和湖南采集17份野葛根际土壤，测定土壤常规理化性质，进行基于MiSeq测序平台的nifH基因高通量测序，采用多元统计分析方法探索固氮微生物群落结构与环境因子之间的关系。【结果】不同采样区域固氮微生物α多样性无显著差异；同一采样区内各样点的固氮微生物群落结构与组成较相似，而不同采样区之间固氮微生物群落结构与组成差异较大，这表明固氮微生物群落存在明显的区域性分布特征。野葛根际土壤中固氮微生物主要归属于变形菌门（Proteobacteria）（相对丰度>60%），在目水平上，已注释出的固氮微生物主要归属于根瘤菌目（Rhizobiales）和伯克氏菌目（Burkholderiales）。根瘤菌目相对丰度在江西采样区最高，伯克氏菌目相对丰度在湖南采样区最高。pH、交换性钙、全钾、海拔和年平均气温对土壤固氮微生物群落结构的影响较大。优势种群伯克氏菌目与pH、交换性钙和全钾正相关，与C/N负相关；优势种群根瘤菌目与pH、交换性钙、海拔和年均温负相关，与全钾和砂粒含量正相关。【结论】不同地理区域野葛根际土壤中固氮微生物α多样性无显著差异，但固氮微生物群落结构与组成存在明显的区域性分布特征。其群落组成受地理环境和土壤理化性质的共同影响，且固氮微生物不同种群对环境因子的响应存在差异。

Abstract:

[Objective] The aims of this study were to clarify the spatial pattern of the nitrogen-fixing microbial community in the rhizosphere of Kudzu (Pueraria lobata), and to explore the relationship between environmental factors and the spatial pattern. [Methods] A total of 17 rhizosphere soil samples were collected from Hunan, Jiangxi, and Guangxi province, where Kudzu was widely distributed. The physical and chemical parameters of the samples were measured by routine methods, and the composition and diversity of nitrogen-fixing microbial community was performed by high-throughput sequencing of nifH gene. Multivariate statistical analysis was used to explore the relationship between the composition of the nitrogen-fixing microbial community and environmental factors. [Results] The α diversity of nitrogen-fixing microorganisms were not significantly different among three sampling regions. The composition of nitrogen-fixing microbial communities were similar in the same sampling region, while were quite different among three sampling regions. It indicated that biogeographical pattern of nitrogen-fixing microbial community was existed. The predominant phylum of nitrogen fixing microorganisms was Proteobacteria, whose relative abundance accounted for more than 60%. At the order level, the species that could be annotated mainly belonged to Rhizobiales and Burkholderiales. The relative abundance of Rhizobiales was highest in Jiangxi, while the relative abundance of Burkholderiales was highest in Hunan. pH, exchangeable calcium, total potassium, elevation and annual mean temperature were the main factors that influenced the composition of nitrogen fixing community. Burkholderiales was positively correlated with pH, exchangeable calcium and total potassium; while was negatively correlated with the ratio of carbon to nitrogen. Rhizobiales was positively correlated with total potassium and the content of sand, while was negatively correlated with pH, exchangeable calcium, elevation and annual mean temperature. [Conclusion] There was no significant difference in the α diversity of nitrogen-fixing microorganisms in the Kudzu rhizosphere soil across different geographical regions; while a clear biogeographical pattern of nitrogen-fixing microorganisms was existed. The spatial pattern of the community was jointly affected by the geographic and soil factors; in addition, the effects of the same environmental factor were distinct for different nitrogen-fixing microbial populations.