不同盐渍化生境野生乌拉尔甘草土壤细菌群落结构及功能预测分析

【目的】探究典型盐生药用植物野生乌拉尔甘草在不同盐渍化生境下土壤细菌群落多样性、组成和功能特征，有助于建立土壤盐分与甘草生长发育、药材品质形成相关的微生物组之间的联系，对栽培甘草药材品质提高具有重要意义。【方法】从野生乌拉尔甘草的6个主分布区采集原生境土壤，采用高通量测序技术比较非盐渍(un-salinization, US)、轻度盐渍(light salinization, LS)、中度盐渍(moderate salinization, MS)以及重度盐渍(heavy salinization, HS)生境中土壤细菌群落多样性、组成及功能的差异，并挖掘不同生境中优势细菌。【结果】野生乌拉尔甘草原生境土壤细菌群落丰富度和多样性在轻度盐渍(LS)组和中度盐渍(MS)组中明显高于非盐渍(US)组、重度盐渍(HS)组，且重度盐渍(HS)组最低。主成分分析(principal component analysis, PCA)表明不同盐渍程度组间的野生乌拉尔甘草土壤细菌群落组成和功能具有显著差异(P<0.05)；冗余分析(redundancy analysis, RDA)表明，土壤盐分(total salt, TS)既是影响原生境土壤细菌群落组成也是影响群落功能的重要因子。属水平，非盐渍(US)组和轻度盐渍(LS)组中的显著优势细菌相同，均为植物有益菌，包括类诺卡氏菌属(Nocardioides)、链霉菌属(Streptomyces)、栖大理石菌属(Marmoricola)；重度盐渍(MS)组中显著优势属既包括有益菌未鉴定_酸杆菌属(unidentified_Acidobacteria)，也包括嗜盐菌盐单胞菌属(Halomonas)、海杆菌属(Marinobacter)；重度盐渍(HS)组中显著优势细菌以嗜盐菌或耐盐菌为主，包括盐单胞菌属(Halomonas)、海杆菌属(Marinobacter)、楚帕氏菌属(Truepera)、别样矿生菌属(Aliifodinibius)、盐坑微菌属(Salinimicrobium)和需盐杆菌属(Salegentibacter)。PICRUSt功能预测分析强调非盐渍(US)组、轻度盐渍(LS)组和中度盐渍(MS)组中的土壤细菌群落与植物互作方面的潜力，表明非盐渍、轻度盐渍和中度盐渍生境中的有益菌对野生乌拉尔甘草生长发育、品质形成具有重要影响。PICRUSt功能预测同时也强调了重度盐渍(HS)组在自我修复适应高盐环境以及参与野生乌拉尔甘草耐盐性提高方面具有潜能，表明重度盐渍生境中的嗜盐菌和耐盐菌对乌拉尔甘草抗盐能力具有重要作用。中度盐渍生境兼具以上二者优势菌群的特征，是值得关注的类型。【结论】野生乌拉尔甘草土壤细菌群落多样性和丰富度在轻度盐渍和中度盐渍生境中明显高于非盐渍和重度盐渍生境；细菌群落的组成和功能在非盐渍和轻度盐渍生境中具有相似性，并与重度盐渍生境存在显著差异，中度盐渍生境兼具以上二者的特征。

Composition and functions of soil bacterial communities of wild Glycyrrhiza uralensis Fisch. in habitats with different degrees of salinization

Objective] We investigated the diversity, composition, and functions of soil bacterial communities of wild Glycyrrhiza uralensis Fisch., a typical halophyte and medicinal plant, in the habitats with different degrees of salinization. The study can help to reveal the linkage between soil salinity and microbiome related to the growth, development, and quality formation of G. uralensis, being essential for improving the quality of cultivated G. uralensis. Methods] Soil samples were collected from six main habitats of wild G. uralensis. High-throughput sequencing was employed to compare the diversity, composition, and functions of soil bacterial communities among the habitats of un-salinization (US), light salinization (LS), moderate salinization (MS), and heavy salinization (HS) and to excavate the dominant bacteria in different habitats. Results] The soil bacterial richness and diversity of wild G. uralensis were higher in LS and MS habitats than in US and HS habitats and were the lowest in the HS group. The principal component analysis (PCA) revealed differences in the composition and functions of soil bacterial communities between groups with different degrees of salinization (P<0.05). The redundancy analysis (RDA) showed that total salinity (TS) was an important factor influencing the composition and functions of the soil bacterial community in the native habitat. The dominant bacterial genera in the US and LS groups were the same, all of which were plant-beneficial bacteria, including Nocardioides, Streptomyces, and Marmoricola. The significantly dominant genera in the MS group included both the beneficial bacteria unidentified_Acidobacteria and the halophilic bacteria Halomonas and Marinobacter. The soil bacteria in the HS group were dominated by salinophilic or salinity-tolerant bacteria, including Halomonas, Marinobacter, Truepera, Alifodinibius, Salinimicrobium, and Salegentibacter. The PICRUSt prediction results underlined the potential of soil bacteria in interactions with plants in US, LS, and MS groups, suggesting that beneficial bacteria in the three habitats influenced the growth, development, and quality formation of wild G. uralensis. Moreover, the prediction results emphasized that the soil bacteria endowed the HS group with the potential of self-repairing for adaptation to highly saline environments and improving the salt tolerance of wild G. uralensis. This result suggested that halophilic and salt-tolerant bacteria in the HS habitat played a key role in the salt tolerance of wild G. uralensis. The MS habitat had both kinds of bacteria, being worthy of attention. Conclusion] The soil bacterial diversity and richness of wild G. uralensis were remarkably higher in LS and MS habitats than in US and HS habitats. The composition and functions of soil bacterial communities in US and LS habitats were similar and differed significantly from those of the HS habitat, and the MS habitat had characteristics of both the above.