Implications of energy and matter fluxes on microbial diversity and complexity in soil systems

微生物群落可以被认为是促进土壤有机质（SOM）周转的中心引擎，从而维持生物地球化学循环和其他重要的生态系统服务。然而，生物多样性对于提供这些服务的重要性仍然知之甚少。本研究项目的目的是表征能量和物质通量对微生物多样性和群落复杂性的影响，以便系统地了解能量和物质如何在土壤中处理。该项目的实验研究特别与DFG SPP2322的三个新的跨学科中央平台实验联系在一起，这些实验旨在阐明不同土壤、基质和边界条件（水势、温度）对能量和物质通量的影响。我们将通过PCR从土壤样品和单个土壤团聚体的DNA中表征微生物种群（细菌，古生菌，真菌）的丰度和多样性，并通过测序16S rRNA基因和ITS扩增子确定其多样性和组成。基于这些数据，我们将表征基质诱导的微生物组的时空变化。此外，我们将把微生物组的信息与物质和能量通量、微生物代谢、生物量和坏死团块池联系起来。我们的数据将通过添加有关土壤微生物群落的丰度、多样性和动态的信息来支持模型数据集成。我们将测试五个假设，以建立微生物多样性与吉布斯能量和底物分子结构在不同土壤和水势和温度变化之间的联系。我们怀疑细菌和真菌群落对能量和物质输入表现出不同的响应，从而代表不同的热力学能量通量通道。这同样适用于寡养和共养细菌。利用我们的分析单个土壤团聚体微生物宏基因组的新协议，我们将试图通过网络分析揭示潜在的群落相互作用模式。此外，通过从凋落物到更深土层的毫米深度梯度，我们将测试通过碎屑层的溶解有机碳扩散是否会产生一个梯度，微生物群对分解的坏死块的贡献增加。最后，我们将利用实验土壤中的粘土梯度来降低几丁质作为坏死团块典型底物的生物有效性，从而改变能量利用并从群落间微生物代谢转变为群落内微生物代谢。总的来说，这个项目的结果应该增强我们对能量和基质如何塑造土壤微生物群以及它们在促进SOM周转方面的效率的理解。

Microbial communities can be considered as the central engine promoting the turnover of soil organic matter (SOM), thereby sustaining biogeochemical cycles and other important ecosystem services. However, the importance of biodiversity for providing these services is still poorly understood. The objective of this research project is to characterize the implications of energy and matter fluxes on microbial diversity and community complexity in order to gain a systems understanding of how energy and matter are processed in soil. The experimental studies of this project are especially linked to the three newly interdisciplinary central platform experiments of the DFG SPP2322 established to elucidate the implications of different soils, substrates and boundary conditions (water potential, temperature) on energy and matter fluxes. We will characterize the abundance and diversity of microbial populations (Bacteria, Archaea, Fungi) from DNA of soil samples and individual soil aggregates by PCR and determine their diversity and composition by sequencing 16S rRNA gene and ITS amplicons. Based on these data, we will characterize substrate-induced temporal and spatial changes of the microbiome. Furthermore, we will link information on the microbiome to matter and energy fluxes, microbial metabolism, biomass and necromass pools. Our data will support model data integration by adding information about the abundance, diversity and dynamics of soil microbial communities. We will test five hypotheses to establish the link between microbial diversity and the Gibbs energy and molecular structure of the substrates within different soils and under variation of water potential and temperature. We suspect that bacterial and fungal communities show distinct responses to energy and matter inputs, thus representing different thermodynamic energy flux channels. This equally applies to oligotrophic and copiotrophic bacteria. Utilizing our new protocol of analysing the microbial metagenome of individual soil aggregates, we will try to unveil patterns of potential community interactions by means of network analyses. Furthermore, following a mm-depth gradient from litter into deeper soil layers, we will test if the diffusion of dissolved organic carbon through the detritussphere creates a gradient with an increasing contribution of microbiomes to the decomposing necromass. Finally, we will utilize a clay gradient in experimental soils to reduce the bioavailability of chitin as a necromass-typical substrate, thereby modifying to energy use and shifting from inter-aggregate to intra-aggregate microbial metabolism. – Overall the results of this project should enhance our understanding how energy and substrates shape the soil microbiome and their efficiency in contributing to the turnover of SOM.