Unravelling the formation of unique modern stromatolites by taxonomic and functional analysis: implications for the early evolution of life

东南极的昂特西湖是一个独特的冰封生态系统，具有超低营养的水域，高pH值，除了阳光(5%)的穿透外，它与环境紧密封闭。这个栖息地是早期地球和太阳系中其他以厚厚的永久冰盖为特征的世界的生态类比，例如土卫二、欧罗巴和火星上古老的冰盖湖泊。它是已知的唯一一个在其底部拥有大型锥形现代叠层石的淡水湖。这些结构由一层薄薄的产氧光合细菌组成，覆盖着沉积物和微生物衍生的有机质的交替片层。目前还不清楚为什么这些大型锥形叠层石只出现在这个地点。我建议使用一种综合的方法来确定这些结构的分类和功能，以阐明推动它们形成的机制。将利用深入的环境分类学、后基因组学和成像分析进行调查，以了解群落的微生物组合和功能潜力。这项研究将调查细菌、真核生物和古生菌在锥形叠层石形成中所起的作用，并了解这些结构是否具有核心分类和功能。为了了解环境和地理的影响，将把昂特西湖叠层石的微生物群组成和功能与类似南极湖泊的微生物结构进行比较。扫描电子显微镜和激光共聚焦扫描将用于探索锥形叠层石中微生物和矿物之间的物理相互作用，并提供有关生物地球化学过程的信息。这项研究将促进我们对微生物垫中复杂结构出现的认识，并对解释生物对古代叠层石的影响是基本的。

Lake Untersee in East Antarctica represents a unique ice-sealed ecosystem with ultra-oligotrophic waters, high pH and it is tightly sealed from the environment except for the penetration of sunlight (5%). This habitat serves as an ecological analog of early Earth and other worlds in our solar system characterized by thick permanent ice covers, such as Enceladus, Europa and ancient ice-covered lakes on Mars. It is the only known freshwater lake hosting large conical modern stromatolites at its bottom. These structures consist of a thin layer of oxygenic photosynthetic Bacteria covering alternating laminations of sediment and microbially derived organic matter. It is still unknown why these large conical stromatolites occur exclusively at this site. I propose to use an integrative approach to determine taxonomy and functionality of these structures to shed light on the mechanisms driving their formation. Investigations to understand the microbial assemblages as well as functional potential of communities will be done using in-depth environmental taxonomic, metagenomic and imaging analyses. This research will investigate the role played by Bacteria, Eukarya and Archaea in the formation of conical stromatolites as well as understanding whether these structures are characterized by a core taxonomy and functionality. Microbiome composition and function of the stromatolites of Lake Untersee will be compared with that of microbial structures in similar Antarctic lakes to understand the effect of environment and geography. SEM and confocal laser scanning will be used to explore physical interactions between microbes and minerals in conical stromatolites and to provide information on the biogeochemical processes involved. This research will advance our knowledge on the emergence of complex structures in microbial mats and is fundamental to interpret biological influences on ancient stromatolites.