N-136. Survival of Methanogens Following Desiccation at Mars Surface Pressure for 60 Days

T. Kral, T. Altheide;
Univ. of Arkansas, Fayetteville, AR.

The relatively recent discoveries that liquid water most likely existed on the surface of Mars and that methane currently exists in the Martian atmosphere have fueled the possibility of extant or extinct life on Mars. One possible explanation for the methane in the Martian atmosphere would be the presence of methanogens in the subsurface. Methanogens are microorganisms in the domain Archaea that can metabolize molecular hydrogen as an energy source, carbon dioxide as a carbon source, and produce methane. One important factor is the arid nature of Mars. Life as we know it requires liquid water, and if it is present on Mars, it may be seasonal just as it is at some locations on our home planet. Here we report on research designed to determine if certain species of methanogens can survive desiccation at Mars surface pressure of 6 mbar, both in a Mars soil simulant, JSC Mars-1, and as naked cells. Methanosarcina barkeri, Methanobacterium formicicum, Methanococcus maripaludis and Methanothermobacter wolfeii were grown in their respective growth media in anaerobic culture tubes. Some of these cultures were added to a sterile Mars soil simulant, JSC Mars-1, some were kept in their sealed anaerobic culture tubes in liquid media, and some were centrifuged followed by removal of the supernatant media. The tubes, with syringe needles inserted through their rubber stoppers, were placed into an environmental simulation chamber. The chamber was sealed and evacuated down to 6 mbar resulting in desiccation of all of the cultures. Desiccation time varied from a few minutes for cultures that were centrifuged to two days for tubes containing liquid media. Following 60 days at 6 mbar, the tubes were removed from the chamber, rehydrated, and placed under ideal growth conditions for the respective methanogens. Cultures of all four organisms that were centrifuged and then maintained as naked cells demonstrated substantial methane production (50 percent or greater), while cultures in JSC Mars-1 demonstrated much less if any methane production. Of the cultures that took two days to desiccate, only M. formicicum demonstrated substantial methane production (approximately 40%).