Table_3_Microbial Diversity of Pinnacle and Conical Microbial Mats in the Perennially Ice-Covered Lake Untersee, East Antarctica.XLSX

Antarctic perennially ice-covered lakes provide a stable low-disturbance environment where complex microbially mediated structures can grow. Lake Untersee, an ultra-oligotrophic lake in East Antarctica, has the lake floor covered in benthic microbial mat communities, where laminated organo-sedimentary structures form with three distinct, sympatric morphologies: small, elongated cuspate pinnacles, large complex cones and flat mats. We examined the diversity of prokaryotes and eukaryotes in pinnacles, cones and flat microbial mats using high-throughput sequencing of 16S and 18S rRNA genes and assessed how microbial composition may underpin the formation of these distinct macroscopic mat morphologies under the same environmental conditions. Our analysis identified distinct clustering of microbial communities according to mat morphology. The prokaryotic communities were dominated by Cyanobacteria, Proteobacteria, Verrucomicrobia, Planctomycetes, and Actinobacteria. While filamentous Tychonema cyanobacteria were common in all mat types, Leptolyngbya showed an increased relative abundance in the pinnacle structures only. Our study provides the first report of the eukaryotic community structure of Lake Untersee benthic mats, which was dominated by Ciliophora, Chlorophyta, Fungi, Cercozoa, and Discicristata. The eukaryote richness was lower than for prokaryote assemblages and no distinct clustering was observed between mat morphologies. These findings suggest that cyanobacterial assemblages and potentially other bacteria and eukaryotes may influence structure morphogenesis, allowing distinct structures to form across a small spatial scale.

南极常年被冰盖覆盖的湖泊提供了稳定且低扰动的环境，在此环境中可形成由微生物介导的复杂结构体。南极东部的乌特瑟湖（Lake Untersee）是一处超贫营养湖泊，其湖底覆盖着底栖微生物垫群落（benthic microbial mat communities），该群落中形成了三种独特的同域层状有机沉积结构体：小型细长尖顶状尖峰、大型复杂锥形结构以及平坦型微生物垫。本研究通过对16S和18S核糖体RNA（rRNA）基因进行高通量测序，分析了尖峰、锥形结构和平坦微生物垫中的原核生物与真核生物多样性，并探究了在相同环境条件下，微生物群落组成如何调控这些独特的宏观微生物垫形态的形成。分析结果显示，微生物群落可依据微生物垫形态呈现显著的聚类分布。原核生物群落以蓝细菌门（Cyanobacteria）、变形菌门（Proteobacteria）、疣微菌门（Verrucomicrobia）、浮霉菌门（Planctomycetes）以及放线菌门（Actinobacteria）为主。尽管丝状齐头藻（Tychonema）在所有类型的微生物垫中均较为常见，但鞘丝藻属（Leptolyngbya）仅在尖峰结构中的相对丰度显著升高。本研究首次报道了乌特瑟湖底栖微生物垫的真核生物群落结构，该群落以纤毛虫门（Ciliophora）、绿藻门（Chlorophyta）、真菌界（Fungi）、丝足虫门（Cercozoa）以及盘嵴亚界（Discicristata）为主。真核生物的丰富度低于原核生物群落，且未观察到基于微生物垫形态的显著聚类分布。上述研究结果表明，蓝细菌群落以及潜在的其他细菌与真核生物可能会影响结构体的形态建成，使得不同的结构体能够在小空间尺度范围内形成。