From single pioneers to complex communities: Simultaneous discrimination of composition and inferring species interactions of fossil as well as modern pro- and eukaryotic microbial communities

该项目的目标是了解土壤中微生物群落的发展，从最初的组装到复杂的网络。在极端环境中，微生物对土壤的发育有着至关重要的影响。土壤微生物对环境变化，如养分增加或温度升高，其群落结构的强烈变化做出反应。由于养分含量低，南极土壤是脆弱的生态系统；它们被认为是环境变化的非常好的早期迹象。我们的核心工作假设包括，原核生物微生物是初始组装中的关键角色，在由各种原核微生物和真核微生物组成的复杂网络中取得成功，该网络基于网络中不同的功能，负责进一步的发展，最终稳定土壤生境。考虑到氮源的生物有效性，真核藻类可能已经在土壤发育的早期阶段就作为先驱相互作用。为了检验这些假设，该项目将把哥廷根大学和波茨坦联邦政府的专业知识联系起来。我们将利用在东南极普里兹湾拉斯曼丘陵的无冰绿洲冰川遗迹前场的五个样点收集的已有样本。彻底分析土壤样品的关键物理化学参数是将微生物多样性与地球化学变量联系起来的关键。考虑到极端的寡营养环境和研究地点的偏远，我们预计将回收相当数量适应良好的迄今未知物种，这是潜在生物技术应用的宝贵来源。我们将时间序列的空间替换方法扩展到微生物胞外和胞内DNA比较的微观尺度。执行一种新的DNA提取方案将能够准确区分灭绝的(化石)和最近活的微生物群落。这两个DNA池将在物种水平上为微生物群落的分类评估服务。最后，通过对来自两个互补和不同可变的rRNA基因签名的扩增片段的深度测序(Illumina MiSeq)，将在物种水平上完成解析。这对于高精度地推断那些促进早期土壤生态系统发展的物种相互作用是至关重要的，即在跨王国和领域的微生物协会内，例如真核藻类和细菌之间。对功能基因的分析将评估碳和氮营养通量中原核微生物群落和真核微生物群落之间的结构和功能关系。最后，在使用定量qPCR估计不同微生物和官能团的相对丰度后，可以推断那些对微生物生产起作用的物种相互作用。

Goal of the project is an understanding of the development of microbial communities in soil, from the initial assembly to complex networks. Microorganisms critically impact the development of soils in extreme environments. Soil microbes react with strong shifts in their community structures on environmental changes, e.g. nutrient increase or temperature raise. Antarctic soils are fragile ecosystems due to their low nutrient content; they are seen to provide very good early indications of environmental change. Our central working hypothesis includes that prokaryotic microorganisms are the key players in the initial assembly succeeding in a complex network of the various pro- and eukaryotic microorganisms which based on different functions within the network is responsible for the further development and, finally, the stabilization of the soil habitat. Eukaryotic algae may interact as pioneers already in the early stages of soil development given the bioavailability of nitrogen sources. To test the hypotheses the project will link the expertise of Göttingen University and GFZ Potsdam. We will utilize already available samples collected at five transects in the forefields of glacier remains in ice-free oases at Larsemann Hills, Prydz Bay, East Antarctica. A thorough analysis of key physicochemical parameters of the soil samples is crucial to relate microbial diversity to geochemical variables. Given the extreme oligotrophic environment and remoteness of the study sites we expect to recover a considerable number of well adapted so far unknown species, representing a valuable source for potential biotechnological applications. We extend the space-for-time substitution approach of chronosequences to the microscale of comparisons between extracellular and intracellular DNA of microrganisms. Performing of a novel DNA extraction protocol will enable a precise distinction between extinct (fossil) and recent live microbial communities. Both DNA pools will serve the taxonomic assessment of microbial communities at the level of species. Finally, through deep sequencing (Illumina MiSeq) of amplicons from two complementary and differently variable rRNA gene signatures resolution at the species level will be accomplished. This is essential to infer those species interactions at high precision which facilitate the development of early soil ecosystems, i.e. within microbial associations across kingdoms and domains, e.g. between eukaryotic algae and bacteria. Analyses of functional genes will assess structure and functional relationships between pro- and eukaryotic microbial communities in nutrient fluxes of carbon and nitrogen. Finally, after estimating the relative abundances of the distinct microbial and functional groups using quantitative qPCR those species interactions can be inferred which act on the microbial production.