Preandean Atacama Desert Endolithic Microbiology

Endolithic ecosystems are considered environmental refuges for life in arid and hyperarid deserts around the world. The microbial communities colonizing these habitats are of special interest due to their ability to live in a polyextreme environment characterized by scarcity of water and extreme solar radiation. The Preandean Depression of the Atacama Desert harbors a number of these endolithic ecosystems, where various substrates are colonized by rich and diverse communities of phototrophic and heterotrophic microorganisms. Recent studies revealed that these communities are dominated by Cyanobacteria, Actinobacteria, Proteobacteria, and Chloroflexi phyla. Studies of the photosynthetic primary producers demonstrated their essential role in supporting the community and uncovered unique adaptation strategies against extreme solar radiation. The diversity found in the endolithic communities of the Preandean Depression, both at the phylogenetic and functional levels, was found to be strongly dependent on water availability and associated with the specific architecture of the substrate. This chapter describes the composition, functioning, and adaptation strategies of microbial communities inhabiting the endolithic substrates found in the Preandean zone of the Atacama Desert. We address the principal biotic and abiotic drivers explaining their diversity from a multidisciplinary perspective.