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

印度尼西亚苏拉威西岛的Towuti湖是一个层状含铁系统，其深盆经历了动态氧化还原条件，在地质时期有不同的氧化铁流入。2015年夏天，ICDP Towuti钻探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，成为埋葬，存档古环境条件。然而，在埋葬过程中改变环境条件将选择特定的微生物群体，从而改变主要的基因组记录。最近的ICDP研究报告对比结果方面的基因组数据重建的古环境条件的适用性。BioMetArchive项目将调查沉积学和地球化学条件如何在沉积时选择特定的微生物组合，并通过1 Ma时间序列对其进行追踪。我们将进一步阐述Towuti湖作为古代含铁系统中微生物过程的现代模拟。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环境和沉积基质，并部分记录在沉积DNA中;（2）深层环境条件选择特定的代谢特征，使地下生物圈能够在托乌蒂湖持续存在，并且与古代含铁系统中的过程相似。沉积物DNA现在可用于从丰度、多样性和代谢功能方面描述微生物种群的特征。BioMetArchive项目将利用2015年野外作业期间以高分辨率采样的沉积物，并在-80 ° C下深度冷冻。最近的测试证明了这种材料对我们计划的分析的适用性。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，以确定控制微生物群落组成的参数。通过宏基因组学，我们将确定哪些微生物类群和代谢特征参与了整个沉积物序列中的铁还原和有机物矿化。最后，我们将重建代谢途径，以驱动铁质沉积物中有效的氧化还原循环和有机物再矿化。沉积物的铁质条件主要选择发酵的深海古菌。分配给这个完全未开垦的门的代谢功能与铁和硫的转化和甲烷生成有关，这表明神秘的地球化学循环。因此，含铁湖Towuti的深层生物圈代表了早期生命代谢过程的现代对应物。

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.