EAGER: Leveraging advances in stable isotope probing to investigate phylogenetic organization in prokaryotic activity

据估计，地球上有超过一万亿种微生物，但其中只有一小部分已被分离出来，在实验室中培养并充分表征。该项目将支持开发一种新方法，将鉴定大量微生物的多样性与其在土壤中消耗不同碳源的作用联系起来，而无需在实验室中分离和培养它们。它将利用DNA测序和环境化学的最新发展。具体而言，本研究还将测试相关微生物是否在土壤中分解相同形式的碳，从而在微生物进化和生态学方面取得重大进展。这项工作还将产生一种重要的新工具来表征微生物生物多样性，以便更好地预测土壤中碳的循环。这个探索性研究（EAGER）项目将通过研究一个完整的生态系统过程：碳分解，来研究进化史在决定微生物功能方面的作用。一种定量测量稳定同位素融入单个微生物“物种”（或种型）核酸的新方法将用于确定哪些微生物正在分解和同化土壤碳库的特定成分。要考虑的土壤碳化合物包括来自植物和微生物的重要代表（例如纤维素，蛋白质），范围从快速矿化（例如葡萄糖和氨基酸）到顽固性（例如纤维素）碳源。比较微生物的活动和系统发育将有助于确定密切相关的生物是否倾向于消耗相同的碳源。为了确定微生物类群和系统发育类群在不同环境条件下的功能作用是否一致，将对不同土壤有机碳特征的土壤进行研究。由于土壤有机碳的数量和化学性质影响微生物群落的组成和活动，这种比较将有助于了解在不同环境条件下哪些生物和活动是一致的。如果发现进化历史是微生物功能的决定因素，则系统发育/功能关系将被表征，以便了解微生物群落的组成如何影响其在生态系统中的功能。除了在环境微生物学领域开辟新领域外，该项目还将支持两名本科生研究人员和一名早期职业研究者。

It is estimated that there are more than one trillion species of microorganisms Earth, but only a small fraction of them have been isolated, grown in the laboratory and fully characterized. This project will support the development of a novel approach that links the identification of the vast diversity of microorganisms with their role in consuming different carbon sources in soil without the need to isolate and cultivate them in the laboratory. It will take advantage of the latest developments in DNA sequencing and environmental chemistry. Specifically, this research will also test whether related microorganisms decompose the same forms of carbon in soil, resulting a major advance in microbial evolution and ecology. This work will also result in an important new tool to characterize microbial biodiversity in order to better predict the cycling of carbon in soil. This Early-concept Grant for Exploratory Research (EAGER) project will investigate the role of evolutionary history in determining microbial function via the study of an integral ecosystem process: carbon decomposition. A novel method that quantitatively measures stable isotope incorporation into the nucleic acids of individual microbial "species" (or phylotypes) will be used to determine which microorganisms are decomposing and assimilating specific constituents of the soil carbon pool. The soil carbon compounds to be considered include important representatives from plants and microbes (e.g. cellulose, proteins) and range from quickly mineralized (i.e. glucose and amino acids) to recalcitrant (i.e. cellulose) carbon sources. Comparing the activity and phylogeny of microorganisms will allow a determination of whether closely related organisms tend to consume the same carbon sources. To determine if the functional roles of microbial phylotypes and phylogenetic groups are consistent under different environmental conditions, soils with differing soil organic carbon characteristics will be studied. As soil organic carbon quantity and chemistry influences the composition and activity of microbial communities, this comparison will provide insight into which organisms and activities are consistent under different environmental conditions. If evolutionary history is found to be a determinant of microbial function, phylogeny/function relationships will be characterized in order to understand how the composition of microbial communities affects their functioning within ecosystems. In addition to charting new ground in environmental microbiology, this project will support two undergraduate student researchers and an early-career investigator.