THE ATACAMA DESERT NORTHERN CHILE: ITS GEOLOGICAL SETTING AND RELATIONSHIP WITH MICROORGANISMS

Northern Chile, between 180 and 270 S, is reputed to be “the driest desert of the world”. It is divided in north-south morphotectonic units climbing dramatically from sea level in the west up to volcanic peaks over 6000 m in the east. Climate changes from extremely arid to hyperarid conditions in the west, to increasingly wetter areas in the east. A number of local base levels corresponding to closed basins constrain or prevent water movement to the ocean. A huge quantity of salts are present in the soils, rocks and waters, as well as an anomalous amount of ore mineral deposits. These conditions define unique yet diverse environments for microorganisms, which make up, for the most part, the entire spectrum of living organisms. We are determining the relationships between these diverse and extreme habitats and the regional geologic, geomorphologic and climatic setting. We have identified organisms of the Bacteria and Archaea domains. Some of them are associated with salt flats and saline lakes where presence of five of the major lineages of Bacteria, plus Holoarchaea and unidentified Euryarchaea, have been detected. In geothermal fields, five bacterial phyla and Euryarchaea and Crenarchaea from the Archaean domain, have been identified. A unique discovery of unicellular cyanobacterias and other eubacterias were found in gypsum structures resembling an “igloo” or sub -spherical shapes between 0.5 up to 1.5 cm diameter, fixed on the surface of rocks as well as in gypsum veins. These initial findings suggest that the region contains a limited, yet diverse, microbial community that has adapted to these unique geochemical habitats.