Andean uncovered biosphere: revealing the vertical miliscale bacterial and eukaryotic community structure and relationships within a microbial mat from Salar de Huasco. Andean uncovered biosphere

igh altitude wetlands of the Chilean Altiplano are unique remote aquatic ecosystems, considered as part of the cold biosphere located at more than 4000 masl. Microbial mats are vertically stratified tridimensional structures shaped by geochemical gradients present in these ecosystems. Diverse microbial communities are embedded in these mucilaginous matrices with specific conditions of oxygen, sulphide and salinity. Here we investigated the upper seven mm layer of a microbial mat from Salar de Huasco, an extreme high-altitude wetland. The diversity of bacteria and eukaryotic microbes distributed through six layers of the mat was analyzed using 454 pyrosequencing of the 16S and 18S rRNA gene. Furthermore, we demonstrate stratified oxygen microprofiles in the microbial mat layer where it has highlighted with clear differences in bacterial community. A total 30,524 bacterial sequences, covering 24 phyla including 15 candidate divisions. At phyla level, semi-rare bacteria were affiliated to WPS-2, Aminicenantes (OP8) and Armatimonadetes (OP10) and almost all the phyla previously clustered to the Candidate Phyla Radiation (CPR). This work focusses on the highly heterogenous microbial community at microbial mat giving a perspective from which the microhabitat extends the microbial diversity. Furthermore, we also expand the knowledge of rare biosphere in a miniature environment highlighting the importance of the low abundance microbial life in the complex and structured microbial mat ecosystem, especially in an extreme and delicate environment founded in the Andean Altiplano.

智利阿尔蒂普拉诺高原的高海拔湿地是独特的偏远水生生态系统，被归入海拔4000米以上寒冷生物圈的范畴。微生物垫（microbial mats）是由该类生态系统中的地球化学梯度塑造而成的垂直分层三维结构体。多样的微生物群落嵌生于这些胶状基质内，所处微环境具备独特的氧、硫化物与盐度条件。本研究针对取自极端高海拔湿地瓦斯科盐沼（Salar de Huasco）的微生物垫上层7毫米区段展开分析。研究人员通过16S与18S rRNA基因的454焦磷酸测序技术，对该微生物垫六个分层中的细菌与真核微生物多样性展开分析。此外，本研究证实该微生物垫层中存在分层氧微剖面，且其特征与细菌群落的显著差异高度关联。本研究共获取30524条细菌序列，覆盖24个菌门，其中包含15个候选分类单元。在菌门分类水平上，半稀有细菌隶属于WPS-2、Aminicenantes（OP8）以及Armatimonadetes（OP10），同时几乎涵盖了此前归类于候选菌门辐射群（Candidate Phyla Radiation）的全部菌门。本研究聚焦于微生物垫内高度异质性的微生物群落，为理解微生境如何拓展微生物多样性提供了全新视角。此外，本研究还深化了对微型生境中稀有生物圈的认知，强调了低丰度微生物在复杂结构化微生物垫生态系统中的关键作用，尤其针对安第斯阿尔蒂普拉诺高原这类极端脆弱的生境而言。