Biology of Desert Endolithic Habitats

Abstract

AbstractIn extreme deserts around the world, endolithic microbial communities find refuge in the interior of semi-translucent rocks as a survival strategy. The pores and fissures of the rock matrix provide a space for colonization, protection from high solar irradiance, and promote the retention of scarce liquid water. Endolithic communities are rather complex ecosystems, spanning multiple domains of life and several trophic levels. These communities are based on the primary production of cyanobacteria, sometime algae, and constituted of an assemblage of heterotrophic bacteria and/or archaea, and viruses. Water availability, in the form of precipitation or relative humidity, is the primary limit on primary production, and thus overall activity in hot and arid deserts. However, other factors such as substrate properties, biotic interactions, and stochastic assembly processes may also influence endolithic community assembly and organization. Metagenomics studies have uncovered that these communities encode for diverse secondary metabolites, including many antimicrobial compounds, suggesting more complex community dynamics than previously thought. Longitudinal studies have revealed the resilience and modes of recovery of endolithic communities to severe climate perturbations but many more studies are needed; arid and hyper-arid deserts, at the dry limit for life, are fragile ecosystems, and their inhabitants will be on the front line of the major changes in climate ahead of us.KeywordsMicrobial communitiesEndolithicMetagenomicsExtreme desertsCyanobacteria