Diversity and functional traits of microbial communities in the terrestrial subsurface habitat along a climatic gradient: from surface into the weathering front at depth

该项目的目标是评估陆地栖息地地下临界带（CZ）的多样性和功能特征，即智利沿海科迪勒拉的EarthShape样带。将测试(1)CZ的陆地地下栖息地是否与地表栖息地相连，从而受气候条件的影响。地球的临界带（CZ）是连接大气和地圈的一层薄薄的生命层。它越来越受到人类活动的影响。含风化带的地下部分是“深层生物圈”的活跃部分，深层生物圈由地球表面以下深处的生境组成。它是地球上最不为人知的栖息地之一。风化过程将坚硬和生物惰性的基岩转变为易碎的风化岩石，这是生物的宜居基质，土壤从中发展。因此，岩石的风化作用对维持地球上的生命至关重要，因为它为生物体提供营养。与岩石相关的生命形式可能在塑造地球以支持生命方面起着至关重要的作用。进一步，本项目将研究(2)深层风化锋的物种多样性和与之相关的微生物风化过程的丰度是否增加。腐岩-基岩界面（风化锋）的微生物群落可能与来自岩石表面的（非光自养）生物具有共同的系统发育起源，而腐岩中与风化过程相关的群落则起源于土壤微生物群落。(3)原核和真核微生物可能形成一个网络，主要驱动风化前沿和深部腐岩剖面的矿物溶解。基于扩增子的元条形码DNA测序方法将实现物种水平上的深度分类学见解。各种功能基因序列将用于推断微生物群落的功能特征，即确定生物量生产和矿物风化活动的丰度和系统发育多样性。将使用一种新的复杂的DNA提取方案，从细胞外DNA池和休眠阶段（细菌内生孢子）的DNA中分离活跃细胞的细胞内DNA。这些努力支持了这样一种假设，即风化锋面在地球形状样带上的发展是最近的特征，并且今天仍在发展。该项目将利用deeppearthshape一揽子计划提出的钻探活动，即沿着干旱梯度在四个研究地点的未风化基岩上钻一个穿过土壤和腐岩的岩心。

Goal of the project is to assess the diversity and functional traits of microbial communities in the subsurface critical zone (CZ) of terrestrial habitats across an aridity gradient, i.e. the EarthShape transect in the Coastal Cordillera in Chile. It will be tested whether (1) the terrestrial subsurface habitat of the CZ is connected with the surface habitat and, therefore, influenced by climatic conditions. The Earth’s Critical Zone (CZ) is a thin living layer connecting atmosphere and geosphere. It is increasingly impacted by human activities. The subsurface part of CZ with the weathering zone is an active part of the “deep biosphere” which comprises of habitats deep beneath the Earth’s surface. It is among the most poorly understood habitats of the earth. Weathering processes transform hard and biologically inert bedrock to a friable weathered rock which is a hospitable substrate for organisms and from which soil develops. Therefore, weathering of rock is crucial for the support of life on earth, as it delivers nutrients to organisms. Rock-linked life forms may occupy essential key roles in shaping the earth to support life. Further, the project will investigate (2) whether species diversity and the abundance of microbial weathering processes related with it increase at the deep weathering front. The microbial communities at the saprolite-bedrock interface (weathering front) may share a phylogenetic origin with (non-photoautotrophic) organisms from rock surfaces, whereas the communities associated with weathering processes in the saprolite have their origin in soil microbial communities. (3) Prokaryotic and eukaryotic microorganisms may form a network that mainly drives the mineral dissolution at the weathering front and in deep saprolite profiles. Deep taxonomic insights at the level of species will be realized by an amplicon-based meta barcoding DNA sequencing approach using paired-end reads. Various functional gene sequences will be employed to infer functional traits of the microbial communities, i.e. to determine the abundances and phylogenetic diversities of biomass production and mineral weathering activities. A novel sophisticated DNA extraction protocol to separate intracellular DNA of active cells from the extracellular DNA pool and DNA of dormant stages (bacterial endospores) will be used. These efforts support evaluating the hypothesis that the advancement of weathering fronts across the EarthShape transect is a recent feature and still evolving today. The project will take advantage of the drilling campaign proposed by the DeepEarthshape package, i.e. to drill a core through soil and saprolite into the unweathered bedrock at the four study sites along the aridity gradient.