BioMetArchive - Subsurface biosphere metagenomics along the 1 Ma sedimentary archive of ferruginous Lake Towuti, Indonesia.

印度尼西亚苏拉威西的Towuti湖是一个分层的含铁系统，其深层盆地经历了动态氧化还原条件，随着地质时间的变化，氧化铁流入变化。2015年夏天，ICDP Towuti钻井项目检索了一份跨越过去1 Ma气候和沉积历史的地层档案。在晚第四纪，干湿交替，导致不同的营养和氧化还原条件。随着沉积物的积累，沉积物表面的微生物生命与金属和有机基质的可用性有关，被埋葬，记录了古环境条件。然而，埋藏过程中环境条件的变化会选择特定的微生物群，从而改变原始基因组记录。最近的ICDP研究报告了关于基因组数据对古环境条件重建的适用性的对比结果。生物档案项目将研究沉积学和地球化学条件如何选择沉积时的特定微生物组合，并通过1 Ma时间序列追踪它们。我们将进一步阐述托乌提湖作为古代含铁系统中微生物过程的现代模拟物。该项目的两个主要假设是：(1)微生物组成最初来自过去的湖泊条件和沉积的基质，并部分记录在沉积的DNA中；(2)深层环境条件选择了特定的代谢特征，这些代谢特征使得托乌提湖的地下生物圈能够持续存在，这些代谢特征与古代含铁系统中的代谢过程相似。由于宏基因组学的最新进展，沉积DNA现在可以用来描述微生物种群的丰度、多样性和代谢功能。BioMetArchive项目将利用2015年野外作业期间高分辨率采样的沉积物，并在-80°C下进行深度冷冻。最近的试验证明这种材料适合我们计划中的分析。我们将建立微生物的系统发育分布，并将基因组数据与现有的环境和地球化学数据集相结合，以确定随时间推移控制微生物群落组成的参数。通过宏基因组学，我们将确定在整个沉积物序列中，哪些微生物类群和代谢特征参与了铁还原和有机质再矿化。最后，我们将重建能够驱动含铁沉积物中有效氧化还原循环和有机物再矿化的代谢途径。沉积物的含铁条件主要选择发酵的深海古菌。这个完全未开垦的门的代谢特征与铁和硫的转化和甲烷生成有关，表明了隐生物地球化学循环。因此，富铁的托乌提湖的深层生物圈代表了早期生命代谢过程的现代对应。

Lake Towuti, Sulawesi, Indonesia is a stratified ferruginous system whose deep basin experienced dynamic redox conditions with variable iron oxide inflows over geologic time. In summer 2015, the ICDP Towuti Drilling Project retrieved a stratigraphic archive spanning the last 1 Ma of climatic and depositional history. During the Late Quaternary, wet and dry periods alternated, resulting in variable trophic and redox conditions. As sediment accumulated, microbial life at the sediment surface, linked to the availability of metal and organic substrates, became entombed, archiving paleoenvironmental conditions. However, changing environmental conditions during burial will select for specific groups of microorganisms, thereby altering the primary genomic record. Recent ICDP studies reported contrasting results with regard to the suitability of genomic data for reconstructions of paleoenvironmental conditions. The BioMetArchive project will investigate how sedimentological and geochemical conditions select for specific microbial assemblages at the time of deposition and trace them through the 1 Ma chronosequence. We will further elaborate on Lake Towuti as a modern analog for microbial processes in ancient ferruginous systems. The two main hypotheses of the project are: (1) Microbial compositions initially arise from past lacustrine conditions and deposited substrates, and are partially recorded in sedimentary DNA; (2) environmental conditions at depth select for specific metabolic features which allow the subsurface biosphere to persist in Lake Towuti and which are similar to processes that operated in ancient ferruginous systems.Thanks to recent advances in metagenomics, sedimentary DNA can now be used to characterize microbial populations in terms of abundance, diversity and metabolic functions. The BioMetArchive project will utilize sediments sampled at high resolution during field operations in 2015 and since kept deeply frozen at -80°C. Recent tests proved the suitability of this material for our planned analyses. We will establish the phylogenetic distribution of microorganisms and integrate genomic data with already existing environmental and geochemical datasets to identify parameters that control microbial community composition over time. Through metagenomics we will identify which microbial taxa and metabolic features are involved in iron reduction and organic matter remineralization throughout the sediment sequence. Finally, we will reconstruct metabolic pathways that can drive efficient redox cycling and organic matter remineralization in ferruginous sediments. The sediment’s ferruginous conditions predominantly select for fermentative Bathyarchaeota. Metabolic features assigned to this entirely uncultivated phylum relate to iron and sulfur transformation and methanogenesis, suggesting cryptic biogeochemical cycling. The deep biosphere of ferruginous Lake Towuti thereby represents a modern counterpart of early life’s metabolic processes.