A synthetic community approach to test how energy and matter fluxes are modulated by trophic interactions and the primary energy substrate in soil

土壤是维持陆地生态系统中生命的关键。然而，描述土壤微生物组的结构和功能多样性及其与更高营养水平的相互作用如何影响土壤中的能量和物质通量的概念框架在很大程度上仍然缺失。我们建议使用一个合成的土壤群落，反映了土壤中的主要微生物类群和微生物食草动物，研究能量和物质输入到土壤，土壤微生物组的结构和功能，以及由此产生的能量和物质通量之间的因果关系。为此目的，设计了一个25个成员的合成土壤群落，包括变形菌，酸杆菌，放线菌，拟杆菌，疣微菌，绿球藻和芽单胞菌以及一个典型的土壤子囊菌的成员。食草动物将以食细菌和食真菌线虫以及食细菌粘细菌为代表。拟议的工作将在两个工作包（WP）中进行。在WP 1中，我们将与其他六个SPP合作伙伴在一个多学科联合研究平台上测试SPP的假设A：微生物组调节能量耗散和物质周转沿着各种能量使用渠道。该提案的重点将是使用合成土壤群落方法分析食菌食草动物和食草动物竞争对微生物组结构以及由此产生的碳通量、碳库和散热的影响。同时，我们将确定食草动物（细菌与真菌）的功能组对微生物组结构，碳通量和散热在自然土壤群落环境中的影响。在WP 2中，我们将使用合成土壤群落方法来检验SPP的假设B：土壤系统中的能量和物质输入、排放和消耗影响生物复杂性。在这里，我们的目标是了解不同的能量产量和降解性（纤维素，淀粉）的模型基质如何影响合成土壤群落的结构，有和没有食草动物的影响。此外，我们将探讨初级能量底物如何塑造微生物组成员表达的化学防御机制（次级代谢产物），并间接影响碳通量和碳池以及散热。我们建议，一个合成的土壤社区将是一个概念驱动的理解土壤中的生态相互作用的重要一步。它将有助于降低天然微生物群落的压倒性复杂性，同时在受控设置中提供定义的结构-功能关系。这种真正的系统生态学方法将有助于理解能量和碳流是如何被土壤微生物组和更高营养水平（WP 1）和主要能量基质（WP 2）调节的。

Soils are essential to sustain life in terrestrial ecosystems. However, a conceptual framework that describes how the structural and functional diversity of the soil microbiome and its interaction to higher trophic levels influences energy and matter fluxes in soil is still largely missing. We propose to use a synthetic soil community reflecting the major microbial taxa and microbial grazers in soil to study causal relationships between the energy and matter input to soils, the structure and function of the soil microbiome, and the resulting energy and matter fluxes. A 25-member synthetic soil community was designed for this purpose consisting of members of the Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Verrucomicrobia, Chloroflexi and Gemmatimonadetes as well as a typical soil ascomycete. Grazers will be represented by bacterivorous and fungivorous nematodes as well as bacterivorous myxobacteria. The proposed work will be performed in two work packages (WP). In WP1, we will test in a joint multidisciplinary research platform with six other SPP partners hypothesis A of the SPP: The microbiome modulates energy dissipation and matter turnover along various energy use channels. The focus of this proposal will be to analyze the effect of bacteria-feeding grazers and grazer competition on the microbiome structure and resulting carbon fluxes, carbon pools, and heat dissipation using the synthetic soil community approach. In parallel, we will identify effects of functional groups of grazers (bacterial vs. fungal) on microbiome structure, carbon fluxes, and heat dissipation in a natural soil community setting. In WP2, we will use the synthetic soil community approach to test hypothesis B of the SPP: Energy and matter input, discharge, and consumption in the soil system affect biological complexity. Here, we aim to understand how model substrates with different energy yield and degradability (cellulose, starch) affect the structure of the synthetic soil community, with and without the influence of grazers. Furthermore, we will explore how the primary energy substrate shapes chemical defense mechanisms (secondary metabolites) expressed by microbiome members and indirectly impacts carbon fluxes and pools as well as heat dissipation. We propose that a synthetic soil community will be an essential step towards a concept-driven understanding of ecological interactions in soils. It will help to reduce the overwhelming complexity of natural microbial communities while providing defined structure-function relationships in a controlled setup. This true systems ecology approach will contribute to understand how energy and carbon flow is modulated by the soil microbiome & higher trophic levels (WP1) and the primary energy substrate (WP2).