Astrobiology of life on Earth.

Astrobiology is often regarded as the study of life beyond Earth, but here we consider life on Earth through an astrobiological lens. Microbiology has historically focused on various anthropocentric sub-fields (such as fermented foods or commensals and pathogens of crop plants, livestock, and humans), but addressing key biological questions via astrobiological approaches can further our understanding of all life on Earth. We highlight potential implications of this approach through the articles in this Environmental Microbiology special issue "Ecophysiology of extremophiles". They report on the microbiology of places/processes including low-temperature environments and chemically diverse saline- and hypersaline habitats; aspects of sulphur metabolism in dysoxic marine waters; thermal acidic springs; biology of extremophile viruses; the survival of terrestrial extremophiles on the surface of Mars; rock-associated microbes and biological soils crusts of deserts; the deep biosphere; and interactions of microbes with igneous and sedimentary rocks. These studies, some of which we highlight here, contribute towards our understanding of the biotic activities and tenacity of terrestrial life. Their findings will help set the stage for future work focused on the constraints for life, and how organisms adapt and evolve to circumvent these constraints. This article is protected by copyright. All rights reserved.