Ectomycorrhizal Mat Communities: Evaluating the Direct Cycling Hypothesis

专门的外生菌根真菌（EcM）在世界各地针叶林和落叶林生态系统的凋落物和土壤中产生广泛的多年生菌丝和根状垫。我们之前的研究表明，这些复杂的微生物群落是微生物活性显著升高的地方，包括养分分解和循环。微生物生态学中最持久的问题之一是在纯培养物中观察到的生理性状与在自然界中观察到或假设的活动之间的差距。利用外生菌根菌垫群落作为离散的实验系统，本研究将试图确定这些生态重要真菌在EcM真菌-宿主树木共生中的具体作用，通过它们利用环境重要的氮和氮的能力腐烂土壤有机质中的磷资源。本研究的具体目标是：1)通过底物氮磷化学变化和胞外酶的产生，评估成垫EcM真菌处理土壤有机质的能力；2)确定EcM真菌如何利用细胞外酶、铁载体或生物表面活性剂作为可能的机制解离活性多酚-蛋白复合物；3)利用纯培养酶的多克隆抗体测定外生菌根对土壤酶活性的贡献。这项研究将有助于理解与土壤微生物系统相关的重要土壤过程。特别是，本研究将阐明土壤生物群从腐烂有机质中释放养分的能力，以及真菌捕获这些资源并促进生态系统中有效养分循环的能力。

Specialized ectomycorrhizal (EcM) fungi produce extensive perennial hyphal and rhizomorph mats in the litter and soil of coniferous and deciduous forest ecosystems around the world. Our previous work has shown these complex microbial communities to be sites of significantly elevated microbial activity, including nutrient decomposition and cycling. One of the most persistent problems in microbial ecology has been the gap between physiological traits observed in pure cultures and observed or hypothesized activities in nature. Using ectomycorrhizal mat communities as discrete experimental systems, this research will attempt to define the specific role of these ecologically important fungi in the EcM fungus-host tree symbiosis through their capacity to exploit environmentally significant nitrogen and phosphorus resources in decaying soil organic matter. The specific objectives of this research are to: 1) assess the ability of mat-forming EcM fungi to process soil organic matter by changes in substrate nitrogen and phosphorous chemistry and the production of extracellular enzymes, 2) determine how EcM fungi dissociate reactive polyphenol-protein complexes using extracellular enzymes, siderophores or biosurfactants as possible mechanisms, and 3) measure the ectomycorrhizal contribution to soil enzyme activities using polyclonal antibodies raised against enzymes from pure cultures. This research will lead to the understanding of important soil processes associated with soil microbial systems. In particular, this study will elucidate the ability of soil biota to release nutrients from decaying organic matter, and the proficiency of fungi to capture these resources and promote efficient nutrient cycling in ecosystems.