Methanogenic Archaea as Model Organisms for Life in Extreme Habitats

Terrestrial permafrost is characterised by extreme environmental conditions, such as sub-zero temperatures, aridity, and long-lasting levels of back-ground radiation as a result of an accumulation over geological time scales. Despite these harsh conditions, terrestrial permafrost is colonized by high numbers of chemoorganotrophic bacteria as well as microbes such as methanogenic archaea.

In the scope of a project in the DFG Priority Program “Mars and the Terrestrial Planets” we contribute to the questions discussed within the field of astrobiology: What are the tolerance limits of microorganisms in extreme environments like terrestrial permafrost and what can we learn from these studies for the search of life in comparable extraterrestrial permafrost habitats like on Mars?

In order to examine these questions, methanogenic archaea derived from Siberian permafrost in addition to known species are used as model organisms to investigate their potential to survive adverse living conditions. Methanogenic archaea are strictly anaerobic microorganisms, which can grow and survive only under anoxic conditions like in permafrost sediments. They are characterized by lithoautotrophic growth, whereby energy is gained by the oxidation of inorganic substances and carbon dioxide can be used as the only carbon source. Lithoautotrophic growth is an important presumption for long-term survival and might be a specific adaptation to the oxygen and organic free environment of early Earth.

The comparative system studies will serve to understand the modern Mars cryosphere and other extraterrestrial permafrost habitats. This knowledge represents an essential basis for searching and understanding of extraterrestrial life, if present, especially concerning possible protected niches on present Mars.