Atacama rock Metagenome. uncultured bacterium

The Atacama Desert, Chile, is the driest and oldest desert on Earth with an estimated age of 90 My. In this study, we describe for the first time chasmoendolithic phototrophic microorganisms associated with heterotrophic bacteria colonizing the fissures and cracks of rhyolite-gypsum and calcite rocks collected in the hyper-arid core of the desert. The use of high throughput sequencing revealed that the Atacama rock communities comprised of a few dominant phylotypes and a number of less abundant taxa representing the majority of the total community diversity. The chasmoendolithic communities were uniquely bacterial, dominated by Chroococcidiopsis species cyanobacteria, and supported a large number of previously unreported phylotypes. Significant differences in community structure and composition were observed between the two rock substrates analysed. Micro-climate data and geomorphic analysis of the rocks revealed enhanced water retention in the complex network of cracks and fissures of the calcite rock and the potential for increased occurrence of liquid water in the form of dewfall, correlating with the more diverse community found within this rock substrate. This study is another example of the diversity of adaptive strategies at the limit for life and illustrates that rock colonization is controlled by a complex set of factors. Samples from rhyolite rocks of volcanic origin, collected in 2010 in the "Lomas de Tilocalar" area (Chile) and calcite rocks, collected in 2010 in the "Valle de la Luna" area (Chile).