The Desert Polyextreme Environment and Endolithic Habitats

Microorganisms that live in extreme environments have recently attracted the attention of scientists worldwide. Among the harshest environments faced by microbial life are hyperarid deserts. The Preandean and Andean “Puna” form part of the Atacama Desert, and these zones are considered the most life-limited places on Earth. As a consequence of two records of extreme environment—the lowest rainfall and highest surface UV radiation/total solar irradiance ever measured on Earth—the Atacama is considered a polyextreme environment. There is evidence today suggesting that successful microbial colonization in this desert, at the limits of microbial life, is the result of a combination of adaptive strategies used by microorganisms to avoid excess solar irradiance and extreme evapotranspiration rates, as they make good use of the rock’s “habitable architecture”. This new concept evokes all the internal structures of a rock that are essential as a habitat for microbial life. This chapter describes the adversity of life conditions and several microbial habitats in the Preandean Depression and Andean region of the Atacama Desert capable of sustaining active microbial ecosystems. All are endolithic habitats (within rocks) providing refuges or islands of life in the desert.