Challenging the survival thresholds of a desert cyanobacterium under laboratory simulated and space conditions

Knowledge of the limit of life’s adaptability to extreme environments is essential for identifying potentially habitable niches in planets and moons in our Solar System or in planetary systems around other stars. Dryness is one of the main life-threatening factors since water removal causes membrane phase transition and production of reactive oxygen species that cause lipid peroxidation, protein oxidation and DNA damage, which are lethal to most organisms. Anhydrobiotic cyanobacteria of the genus Chroococcidiopsis possess a remarkable resistance to desiccation and radiation; as such they have extended the limits of life as we know it in several new directions. Investigating the threshold of such resistance can help us in understanding not only the limits of life on Earth but also in assessing the potential habitability of Mars, of icy moons, and of exoplanets characterized by high doses of radiation and transient availability of liquid water. New insights have been provided by experiments exposing cyanobacteria to laboratory simulations that mimic planetary conditions, and also to real space conditions.