An Extreme life: Eu-endolithic microbes surviving within modern microbialites at High-Altitude Lakes in Argentinean Puna (4,000 m asl).

ALBARRACIN VIRGINIA H.; MORENO JULIO; TONEATTI DIEGO; POIRE DANIEL G.; FARIAS MARIA EUGENIA

Ginebra

Congreso; 4rd FEMS Congress of European Microbiologists; 2011

FEMS

Background. High-Altitude Andean Lakes (HAAL) at Argentinian-Puna-High Andes (between 3,000 to 6,000 m) are exposed to extreme conditions: volcanic settings, high UV-irradiation, hypersalinity, desiccation, high pH. An outstanding microbial biodiversity has developed, most of them ordered in multi-layered sedimentary mats called microbialites. These kind of ecosystems were common in ancient marine environments but today restricted to few lacustrine and perimarine settings. Compared to them, those from HAAL are the only ones that exist under such hostile environmental conditions resembling those that prevailed at the early Earth. Aim. To characterize the eu-endolythic microbiota from extreme microbialites at Lake Socompa (SST; 4000 masl, pH 9, salinity: 8.3%, 35 mgL-1 As), Lake Diamante (DMT; 4650 masl, pH 11, salinity: 11.9%, 230  mgL-1 As), and “Sea Eyes” Tolar (TMT; 3,600 masl, pH 7.2, salinity: 13.2%, 0.6 mgL-1 As), Northwest-Argentina.  Methods. Samples were taken aseptically and fix in situ to perform further mineral characterization by X-ray diffraction and optical and scanning electron microscopic. Results. Socompa microbialites can be classified as typical stromatolites as the main complexing-mineral was Aragonite. TMT and DMT are mainly composed by Gypsum and Halite while Gaylussite was found only in DMT. We observed bacteria and algae (cyanobacteria and diatoms) agglutinated by exopolysaccharides and associated to minerals, presenting typical microboring patterns produced by bacteria. Conclusion. These different types of microbialites found at the highlands are of utmost interest as they provide a model to study ecology and biogeochemistry of their Precambrian counterparts in a very similar environment to the Early Eath´s one.