SRP007748 Socompa Stromatolite STROMATOLITES AT SOCOMPA LAKE: MICROBIALCOMMUNITIES DEVELOPING UNDER ALKALINE, HIPERARSENIC AND HIPERSALYNE VOLCANIC ASSOCIATED ECOSYSTEM OVER 4000 M IN THE ARGENTINEAN PUNA The High-Altitude Andean Lakes (HAAL) in the Argentinian Puna-High Andes region represent an almost unexplored ecosystem of shallow lakes at altitudes from 3,000 to 6,000 m. Although exposed to extreme conditions: i.e. volcanic settings, high UV irradiation, hypersalinity, drastic temperature changes, desiccation, and high pH, an outstanding microbial biodiversity has developed, most of them ordered in multi- layered flat mats and stubby pillars called microbialites. Calcareous cyanobacterial microbialites defined as stromatolites and thrombolites were common in ancient shallow marine environments. Today, they are restricted to a few lacustrine and perimarine settings. Compared to them, those from HAAL are the only ones that exist under such hostile environmental conditions. Moreover, they experience environmental conditions resembling those that prevailed at the early Earth, making their study even more promising as a modern template of Early Life development. The present dataset of bacterial diversity assessed by pyrosequencingV4 region of 16S rRNA gene correspond to the first observation of extreme microbialites harboring a diverse eu-endolythic microbiota at Laguna Socompa (4000 m asl, pH 9; salinity: 83 ppm; 35 mg L-1 As) at the bottom of Socompa Volcano Northwest Argentina. Socompa Stromatolite Bacterial Diversity DNA from Stromatolite was extracted. 16S rDNA was amplified using RDP designed primers and where sequenced using 454 titanium chemistry, obtaining 113,255 high quality-filtered sequences.