ALBERT

Description: The environmental conditions of early Mars and early Earth are assumed to have been most similar. The oldest proofs of life on Earth, which can be found as microfossils in Archaean rocks, date back to this time of about 3.8 Ga ago. Regarding this one can presume that life might have evolved on Mars, too. Martian life must have adapted to the drastic change of conditions on the planet or become extinct. Plausible forms of still existing prokaryotic life on Mars are lithoautothrophic subsurface ecosystems. Comparable environments exist in the permafrost regions on Earth.On Mars frozen water in form of surface glaciers and subsurface ground ice layers but also water in a liquid state - which is one of the most important factors for the existence of life - could be observed by NASA and ESA missions. The detection of methane on Mars by Mars Express lead to the conclusion that it must be of a recent origin because of its rather short persistence time in the atmosphere of a few hundreds of years. Thinkable sources of the methane are active volcanism - that could not yet be observed on modern Mars - or biogenic production. The correlation between the presence of water vapour and methane on the Martian surface which occur both in higher concentrations in the same regions and time intervals are an indication of a biological source of the methane on Mars. Methanogenic archaea from terrestrial permafrost regions are therefore one of the most suitable candidates for possible existing life on Mars. They have evolved under early Earth conditions, grow lithoautotorphicly under strictly anaerobic surroundings, are able to tolerate low temperatures and have survived in the extreme environments of permafrost affected soils for several millions of years.This PhD project is associated to the Helmholtz-Alliance Planetary Evolution and Life and is focused on experiments with strains of methanogenic archaea that have been isolated from the active layer of permafrost on Samoylov Island in the Lena Delta, Siberia. Former experiments with these strains revealed significantly higher survival rates compared to non-permafrost strains after the exposure to a simulated Martian diurnal profile with alternating temperatures between -75°C and +20°C, humidity from 0.1 to 0.9 aw and a Mars-like gas composition and pressure (Morozova et al., 2007). In the current work it will be examined if the methanogenic archaea from permafrost do not only survive simulated Martian conditions but rather are able to show an active metabolism. Also the effects of mars analog minerals in form of artificial soils and the contribution of biofilm formation on the activity, survival and water retention capability of these organisms is to be investigated.A first growth test with artificial soils added in concentrations between 0.0 and 5.0% to the culture media was performed with permafrost and non-permafrost strains as a reference with incubation temperatures of 10 and 28°C. Tested Mars analog minerals were JSC-Mars-1A, Early Acidic Mars and Late Basic Mars. The results showed an increase of methane formation rates measured via gas chromatography for all strains after adding small amounts of soil analoges for all tested minerals at both temperatures. Higher amounts of minerals leaded to lower methane formation rates or had no significant effect. Only for the permafrost strains an increase of the methane formation rates at 10°C could be observed with 5.0% of Late Basic Mars compared to lower mineral concentrations. The activity of the methanogenic archaea under simulated Martian conditions is to be determined via measuring of their methane production. Therefore a laser system based on wavelength modulation spectroscopy will be used, which can be attached to a simulation chamber where the strain samples can be exposed to the specific Mars analog conditions.To study the limits that are necessary for methanogenic archaea from terrestrial permafrost regions to maintain their activity with simulation experiments helps to understand more about the possibilities for life in the Martian cryosphere as well as in other potential extraterrestrial permafrost habitats.

Description: Five strains of methanogenic archaea isolated from two extreme habitats had been characterized for their physiological and phylogenetical properties. The strains SMA21 and SMA17 were isolated from the permafrost soil of the Lena river delta, Siberia and the strains MC15, MC20 and MC21 were isolated from the anaerobic sediment of the subsurface lake of Movile Cave, Romania, which contains a chemoautotophically based ecosystem with several endemic species.The strains SMA21 and SMA17 were irregular cocci whereas strain MC15 formed sarcinalike cocci in aggregates. The strains MC20 and MC21 were rodshaped. All strains grew within a temperature range from 0 up to 44°C, a pH value of 6.2 to 9.9 and salt concentrations from 0.02 to 0.6 M NaCl. Some were also able to grow at lower pH values down to pH 4.8 for SMA21, SMA17 and MC21 and even down to pH 4.1 for MC15. The most of the strains grew also at higher temperatures up to 54°C except MC20. The substrates used for methane formation were H2/CO2, methanol and acetate for the coccishaped and H2/CO2 and formiate for the rodshaped strains. MC20 could also use 2-propanol. Trypicase peptone and yeast extract were not needed for growth by any strain.The 16S-rRNA fragment sequences of the strains MC20 and MC21 could be allocated to the genus of Methanobacteria and the sequences of the strains MC15, SMA17 and SMA21 to Methanosarcina. The sequence of MC20 showed only 96.7% similarity to the sequence of the nearest cultivated relative Methanobacterium oryzae, which indicates for a discrete species. MC15 and MC21 showed a slightly higher similarity difference of 98.5% to Methanosarcina barkeri and 99.4% to Methanobacterium subterraneum, respectively. The strains SMA17 and SMA21 showed a high similarity to each other and to their nearest cultivated relative Methanosarcina mazei (99.8 and 99.9%), but with significant differences in their physiological properties.