第308期 文献解读-柳枝稷根际原生生物多样性和群落复杂性随其发育而变化

杂志- Microbiome

影响因子-14.00

发表时间-2021

摘要：

背景：尽管原生生物分布广泛且在生态学上具有重要作用，但它们仍然是土壤和根际微生物组中最不为人知的组成部分之一。关于原生动物在刺激有机物分解和塑造微生物组动态方面的作用的知识不断增加，但仍然需要了解生物和环境因素介导原生动物群落组装和动态的程度。我们假设，原生动物群落受到植物对其根际生物和物理化学环境的影响，导致原生动物多样性和组成的模式，反映了以前观察到的根瘤细菌群落的多样性和演替动态。

结果：我们分析了柳枝稷（SG）植物（Panicum virgatum）在不同物候期的根际土和非根土相关的原生生物群落，这些植物生长在两个边缘土壤中，是大规模田间实验的一部分。研究结果显示，根际土中原生动物的多样性低于非根土，时间上的变化取决于土壤性质，但在根际土中不太明显。根际土中明显流行的原生动物群体的模式表明，大多数原生动物在植物生长阶段发挥不同的生态作用，一些植物病原性原生动物和杂食性原生动物在根际土中长期重复出现。我们发现，与非根土相比，根际土中的原生动物共生网络动态更为复杂。基于系统发育的空模型分析表明，在我们的研究地点，原生动物的群落组合主要受同质选择和扩散限制的控制，随着柳枝稷的生长和衰老，根际土中的选择比非根土更强。

结论：我们证明，环境过滤是决定原生动物群落总体特性的主要因素，在根际土中，植物对物理和生物环境的控制是原生动物群落组成和动态的关键驱动力。由于原生动物是植物营养供应和细菌群落组成和丰度的关键贡献者，绘制和理解它们在根际土中的模式是理解根-微生物-土壤系统的生态学的基础。

关键词：原生生物，微生物组，柳枝稷，根际，群落组装

 Fig. 4 a Succession of rhizosphere and bulk soil networks for protist communities over time. The five sampling points corresponded with different developmental stages of switchgrass plants in two sampling sites. Networks represent RMT co-occurrence models from biological replicates (minimum of 10) at each sampling point, where nodes represent ZOTUs or exact sequence variants, and links between nodes represent significant correlations. Modules are randomly colored. Red and blue links represent significant negative and positive correlations. b Network topological parameters for both sites over time for bulk and rhizosphere protists networks. SL = sandy loam site, CL = clay loam site

Fig. 5 Relative importance of different ecological processes in protist community assembly. a Dispersal limitation and homogenous selection were the most influential ecological processes in both sampling sites for bulk soil and rhizosphere communities across sampling times. B Comparison between bulk soil and rhizosphere show that rhizosphere protists are under higher homogeneous selection but lower dispersal limitation during the growth and/or senescence of switchgrass. Significance is based on bootstrapping with 1000 replications. *P < 0.1; **P < 0.05; ***P < 0.01

原文信息：

Title: Protist diversity and community complexity in the rhizosphere of switchgrass are dynamic as plants develop

Abstract:

Background: Despite their widespread distribution and ecological importance, protists remain one of the least understood components of the soil and rhizosphere microbiome. Knowledge of the roles that protists play in stimulating organic matter decomposition and shaping microbiome dynamics continues to grow, but there remains a need to understand the extent to which biological and environmental factors mediate protist community assembly and dynamics. We hypothesize that protists communities are filtered by the influence of plants on their rhizosphere biological and physicochemical environment, resulting in patterns of protist diversity and composition that mirror previously observed diversity and successional dynamics in rhizosphere bacterial communities.

Results: We analyzed protist communities associated with the rhizosphere and bulk soil of switchgrass (SG) plants (Panicum virgatum) at different phenological stages, grown in two marginal soils as part of a large-scale field experiment. Our results reveal that the diversity of protists is lower in rhizosphere than bulk soils, and that temporal variations depend on soil properties but are less pronounced in rhizosphere soil. Patterns of significantly prevalent protists groups in the rhizosphere suggest that most protists play varied ecological roles across plant growth stages and that some plant pathogenic protists and protists with omnivorous diets reoccur over time in the rhizosphere. We found that protist co-occurrence network dynamics are more complex in the rhizosphere compared to bulk soil. A phylogenetic bin-based null model analysis showed that protists’ community assembly in our study sites is mainly controlled by homogenous selection and dispersal limitation, with stronger selection in rhizosphere than bulk soil as SG grew and senesced.

Conclusions: We demonstrate that environmental filtering is a dominant determinant of overall protist community properties and that at the rhizosphere level, plant control on the physical and biological environment is a critical driver of protist community composition and dynamics. Since protists are key contributors to plant nutrient availability and bacterial community composition and abundance, mapping and understanding their patterns in rhizosphere soil is foundational to understanding the ecology of the root-microbe-soil system.

Keywords: Soil protist, Soil microbiome, Switchgrass, Rhizosphere, Community assembly

解读人：缪雨静