Isolation and Characterization of extremophiles from saline environments and their astrobiological relevance

Abstract

The aim of this study was to investigate samples isolated from extreme saline habitats and test them for their potential to survive Mars-like conditions. This was tested by performing radiation experiments including UV-C and X-ray radiation, as well as desiccation experiments. Extremophilic organisms like Haloarchaea and spore-forming bacteria can survive under extreme conditions on Earth and could thus be a promising start to explore their abilities outside the planet Earth. The Salar de Uyuni in Bolivia and the Lüneburger brine were chosen to isolate such extremophiles, as both habitats show an extreme salt concentration. Within this thesis, a total of 65 microbial isolates were obtained, belonging to 26 different species from the families of Haloarculaceae, Haloferacaceae, Natrialbaceae, and Bacillaceae. The species Haloarcula japonica and Bacillus aerius were tested for radiation resistance. 8% of Bacillus aerius cells were found to be able to survive radiation of 500 Gy and 0.1% of cells could survive 500 J m⁻², whereas 9% of cells of Haloarcula japonica survived 500 Gy and only 0.02% of cells survived 500 J m⁻². The species Natromonas moolapensis was tested towards desiccation resistance and continued to show a survival of 10% after nine days of desiccation. This study provides a basis for further research regarding potential life in outer space, by exploring extremophiles on Earth and their ability to survive extreme radiation and salt concentrations in their environment.