Extreme halophiles (halobacteria) are microorganisms that require a high concentration of NaCl for their optimal growth. They belong to the domain Archaea, together with methanogens and some thermophiles. It has been shown that halobacterial cells are entrapped within the fluid inclusions when NaCl crystallizes, and viable cells could be recovered after many months. Many halobacteria have been isolated from Permian halite, however, few studies are generally accepted due to questions about sample quality and contamination.
A recent report that a halophilic bacterium was isolated from a fluid inclusion within a primary salt crystal of the Permian (250 Ma) suggested again that previously reported isolations of halobacteria from Permian halite might be true. The requirement for elevated salt concentration, the probable ability to survive within low water activity environments for long period, and the presence of concentrated KCl in the cells, which is shown to protect DNA and proteins from harmful irradiation, makes halobacteria likely candidates for life on early Mars.
