土壤理化性质驱动烤烟根际细菌群落的组配及其共现性网络互作

Soil properties affect bacterial community assembly and co-occurrence network in tobacco rhizosphere

摘要:

【目的】解析土壤微生物在植物根际的组配机制对于认识和维护农田生态系统的稳定性至关重要。【方法】通过Illumina高通量测序和生物信息学分析方法明确了我国主要种植烟草生态区烤烟根际土壤细菌群落与土壤理化性质的互作关系。【结果】烤烟根际细菌类群主要为放线菌纲（Actinobacteria）、α-变形菌纲（Alphaproteobacteria）、γ-变形菌纲（Gammaproteobacteria）和嗜热油菌纲（Thermoleophilia）。细菌群落组成按生态区聚类，且样本空间距离和细菌群落相似度显著负相关。共现性网络分析表明，烤烟根际细菌群落间协同作用大于拮抗作用，武陵秦巴生态区、黄淮平原生态区、南岭丘陵生态区和沂蒙丘陵生态区细菌群落高度模块化，小单胞菌属（Micromonospora）为南岭丘陵生态区和黄淮生态区细菌共现性网络的网络中心，Bryobacter和气单胞菌属（Arenimonas）为南岭丘陵生态区细菌网络的模块核心，其菌群特性而非相对丰度决定了其在稳定细菌网络中的重要作用。冗余分析结果证实pH、有效铁、交换性镁和有效锰能显著影响烤烟根际细菌群落结构。【结论】烤烟根际细菌群落在pH、有效铁、交换性镁和有效锰等土壤理化性质驱动下呈现出均质化和生境特异性的特点，小单胞菌属、Bryobacter和气单胞菌属在烤烟根际细菌群落中发挥重要作用。

关键词:细菌群落;共现性网络;烤烟;根际;生境特异性

Abstract:

[ Objective] To understand the contribution of microbial community assembly in plant rhizosphere to the stability of farmland ecosystem. [ Method s] High-throughput sequencing and bioinformatics tools were employed to explore the relationship between the bacterial community in tobacco rhizosphere and soil properties in the eight major tobacco-planting ecotopes in China. [ Result s] The most abundant bacterial classes were Actinobacteria, Alphaproteobacteria, Gammaproteobacteria, and Thermoleophilia. The composition of bacterial community presented a clustering pattern according to ecotopes, and the similarity of bacterial community among samples had a significantly negative correlation with spatial distance. The co-occurrence network of bacterial interactions indicated a higher proportion of positive links than that of negative links between bacteria. The network of Wuling-Qinba mountains (WQM), Huanghuai plain (HHP), Nanling hills (NLH), and Yimeng hills (YMH) presented high modularity. Micromonospora as the network hub in NLH and HHP contributed to the stability of microbial network. Bryobacter and Arenimonas were identified as module hubs in NLH and their characteristics rather than relative abundance determined their role in stabilizing bacterial co-occurrence network. The results of redundancy analysis showed that pH, available iron (availFe), exchangeable magnesium (exchMg), and available manganese (availMn) remarkably affected the bacterial community assembly in tobacco rhizosphere. [ Conclusion ] The homogenization and habitat specificity of bacterial community assembly in tobacco rhizosphere were affected by soil pH, availFe, exchMg, and availMn. Micromonospora, Bryobacter, and Arenimonas played an important role in the bacterial community of tobacco rhizosphere.

Key words:bacterial community assembly;co-occurrence network;tobacco;rhizosphere;habitat specificity