Experimental approach to the screening of prokaryotic assemblage in Antarctic permafrost

Permafrost covers more than 25% of the Earth's surface. It is extremely sensitive to global climate warming and its degradation could have dramatic impacts on the entire Earth system (Panikov et Sizova 2007). Permafrost hosts a potentially large pool of microorganisms, which is supposed to be the only life forms known to have retained viability over geological time. Thawing of the permafrost renews their physiological activity and exposes ancient life to modern ecosystems (Gilichinsky et al. 2008). The adaptation mechanisms of microorganisms, at species or population level, make them susceptible to extreme environmental condition. The survival of microorganisms in permafrost raises the question of what constitutes the limit for microbial life. Several studies of microbial populations have been conducted in Arctic or Antarctic permafrost (Guglielmin et al. 2005), but few studies concern the prokaryotic assemblage. Our contribution aims at filling some gaps in the knowledge about this peculiar and till now poorly studied microbial assemblage, evaluating the experimental methods to investigate it in terms of abundance, viability, ectoenzymatic activities and physiological profiles at community level.