Collaborative Research: Microbial necromass decomposition: moving from predictions to principles

越来越多的人认识到微生物是土壤中有机质积累的重要贡献者，通过它们自己的死细胞物质的输入，统称为坏死团块。尽管在量化影响坏死团分解速率的生态因素方面取得了进展，但实际上是哪些微生物驱动了这种周转，以及不同官能团之间的相互作用如何影响降解动力学仍然知之甚少。本研究的总体目标是从功能上描述细菌和真菌如何单独或共同降解微生物坏死物，以及坏死物中的碳和氮如何进入不同的生态系统池（土壤和植物）。该研究团队的跨学科优势将提供对分解者群落功能如何以与重要生态系统服务（如土壤碳储存和植物养分获取）直接相关的方式影响微生物坏死块分解的整体理解。除了加强我们对坏死团相关微生物群落功能的理解外，该项目还开展了多项具有更广泛影响的活动，重点是与公众分享知识，并培训多样化的stem学生。具体的研究目标包括：目标1：利用充分研究的真菌和细菌分解系统表征微生物坏死块降解的基因和代谢途径；目标2：确定哪些土壤微生物利用来自微生物坏死块的资源，以及它的分解如何影响土壤碳和氮库；目标3：跟踪树木如何通过外生菌根真菌共生获得微生物坏死块来源的氮。这些目标将通过一套从个体微生物培养到复杂群落的综合实验来解决。在第一个目标中，基于rnaseq的实验室实验将生成真菌坏死块在生态相关和多样化的真菌和细菌中腐烂过程中的基因表达的详细资料。第二个目标是将qSIP分析与周围土壤和根系的同位素分析（使用IRMS和NanoSIMS成像）相结合，定量跟踪从腐尸块类型向不同生态系统池释放的碳和氮。最后，在目标3中，将对实验室培养的坏死块上存在的微生物群落进行实验操作，以研究初始底物化学和种间竞争如何影响外生菌根真菌向树木转移坏死块氮的量。总的来说，这项研究试图将微生物坏死块分解的研究从一个很大程度上描述性的过渡到一个机械预测性的科学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Microorganisms have been increasingly recognized as significant contributors to the accumulation of organic matter in soil through the inputs of their own dead cell material, collectively referred to as necromass. Despite progress in quantifying the ecological factors affecting the rates of necromass decomposition, which microorganisms actually drive this turnover and how interactions among different functional groups affect degradation dynamics remains poorly understood. The overarching objective of the proposed research is to functionally characterize how bacteria and fungi, both alone and together, degrade microbial necromass and how the carbon and nitrogen from necromass moves into different ecosystem pools (both soils and plants). The cross-disciplinary strengths of the research team will provide a holistic understanding of how decomposer community functioning influences microbial necromass decomposition in ways directly relevant to important ecosystem services such as soil carbon storage and plant nutrient acquisition. Along with enhancing our understanding of the functioning of necromass-associated microbial communities, the project has multiple broader impacts activities focused on sharing knowledge with public audiences and training a diverse pool of STEM-focused students. The specific research aims include: Aim 1: Characterize the genes and metabolic pathways involved in microbial necromass degradation using well-studied fungal and bacterial decomposition systems; Aim 2: Determine which soil microbes use resources derived from microbial necromass and how its decomposition affects soil carbon and nitrogen pools; Aim 3: Track how trees acquire microbial necromass-derived nitrogen via ectomycorrhizal fungal symbioses. These aims will be addressed through an integrated set of experiments that scale from individual microbial cultures to complex communities. In the first aim, RNAseq-based lab experiments will generate a detailed profile of gene expression during the decay of fungal necromass in an ecologically relevant and diverse set of fungi and bacteria. The second aim will couple qSIP analyses of the microbial communities on field-based decaying necromass with isotopic analyses of surrounding soils and roots (using both IRMS and NanoSIMS imaging) to quantitatively track carbon and nitrogen release from necromass types into different ecosystem pools. Finally, in Aim 3, microbial communities present on lab-incubated necromass will be experimentally manipulated to examine how initial substrate chemistry and interspecific competition affect the amount of necromass nitrogen transferred to trees by ectomycorrhizal fungi. Collectively, this research seeks to transition the study microbial necromass decomposition from a largely descriptive to a mechanistically predictive science.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.