Evaluation and quantification of microbial degradation of allochthonous organic matter by "priming" (MicroPrime)

该项目的主要目标是通过微生物机制来表征水生碳循环的未来变化，特别是通过关注在水生生态系统中很少研究的启动效应。根据环境条件的不同，引发剂可以刺激或抑制微生物的c循环。因此，我们的目标是通过化合物特异性稳定同位素分析（例如微生物磷脂脂肪酸（PLFA）中的13C/12C比率）在现场和实验室实验中揭示引物作用的未来变化。我们打算开发合适的方案，将PLFA分析与分子方法相结合，例如稳定同位素探测（DNA-SIP; RNA-SIP），特别是细菌和真菌。本研究旨在确定受全球变化影响的水生系统中，陆源OC输入对启动效应的影响，从而对水陆耦合及其对碳循环的作用。据我们所知，这将是第一个通过一种方法测试不稳定OC和顽固性OC池中13c标记OC的代谢转移的研究，从而研究水生生态系统中启动效应的潜在机制。两个c池将提供不同的脉冲制度和营养条件，以揭示不稳定OM有效性对顽固性有机质（OM）降解过程的影响。在第一阶段，将进行实验室实验，由具有明确特征的降解确定底物能力的确定微生物组成，从而能够研究基本机制、生物体之间的相互作用及其对OM降解的作用。特别强调真菌在水生矿化过程中的作用。我们首先想要阐明这些过程中细菌和真菌的启动、协同效应的基本机制，并量化哪些部分的om池（不稳定的vs.顽固性的）被呼吸或被微生物生物量吸收。在第二阶段，将利用自然群落、C添加的不同时间过程（脉冲模拟水生系统中更频繁的C输入）和介质中的不同营养条件（元素化学计量学），研究具有特征的基本机制和生物相互作用在OM循环中的作用。在第三阶段的后期，这些研究将通过使用介观宇宙实验扩展到更复杂的环境条件（http://www.lake-lab.de/）。在这里，我们主要想挑战我们在环境条件下从第一阶段和第二阶段获得的知识，特别是在自然条件下解决颗粒通量问题。我们的模块化方法将使我们能够阐明启动在水柱以及水陆界面的c循环中的作用，从而改善水生系统中的c预算。

The main goal of this project is to characterize future changes in aquatic C-cycling via microbial mechanisms, in particular by focusing on priming effects, which have been little studied in aquatic ecosystems. Depending on environmental conditions, priming can either stimulate or inhibit microbial C-cycling. Therefore, we aim to unravel future changes in the role of priming via compound specific stable isotope analysis (e.g. 13C/12C ratio in microbial phospholipid fatty acids (PLFA)) both in field and laboratory experiments. We intend to developing suitable protocols to combine PLFA analyses with molecular methods, e.g. stable isotope probing (DNA-SIP; RNA-SIP), in particular for bacteria and fungi. This study aims to determine the impact of terrigenous OC input on priming effects, and hence on the aquatic-terrestrial coupling as well as their role for C-cycling in aquatic systems affected by global change. To our knowledge, this will be the first study testing for the metabolic transfer of 13C-labled OC from both, labile and recalcitrant OC-pools in one approach and hence investigating the underlying mechanisms of priming effects in aquatic ecosystems. Both C-pools will be supplied with different pulsing-regimes and nutrient-conditions to unravel effects of labile-OM-availability on recalcitrant organic matter (OM) degradation processes. In the first phase, laboratory experiments consisting of defined microorganisms with well characterized abilities to degrade defined substrates will be carried out and thus enable studies on basic mechanisms, interactions between organisms and their role for OM degradation. Special emphasis will be set on the role of fungi in aquatic mineralization processes. We first want to elucidate basic mechanisms concerning priming, synergistic effects of bacteria and fungi in these processes and quantify which parts of the OM-pool (labile vs. recalcitrant) are respired or incorporated into microbial biomass. In a second phase, the role of characterized basic mechanisms and organism-interactions for OM cycling will be studied using natural communities, different time courses of C-additions (pulsing to simulate more frequent inputs of C in aquatic systems) and different nutrient conditions in the medium (elemental stoichiometry). Later in a third phase, these studies will be extended to much more complex environmental conditions by using mesocosm-experiments (http://www.lake-lab.de/). Here we mainly want to challenge our gained knowledge from phase one and two under environmental conditions, in particular addressing particle fluxes under natural conditions. Our modular approach will enable us to elucidate the role of priming in C-cycling in the water column as well as at aquatic-terrestrial interfaces and hence to improve C-budgets in aquatic systems.