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

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.