Even very low microbial activity within permanently frozen ground could have a tremendous impact on geochemistry and geophysics of cryolithozone on a geological time scale of 103-104 years. In seasonally frozen winter soils, microbial activity could be an important agent of biochemical transformations, leading to restoration of soil fertility and resuscitation of stressed and metabolically injured cells (one of the reasons for the frequently observed spring burst of soil activity). There is increasing concern from conservational microbiologists that global warming might damage the most vulnerable psychrophilic members of the soil community. System analysts involved in the construction of a holistic view of the Earth under anticipated global changes can no longer ignore subzero microbial activity, which should be incorporated into comprehensive simulation models of terrestrial and marine ecosystems for the better understanding and realistic prediction of climatic changes.
Microbial subzero activity is also important for astrobiological studies and bio-technological developments. Evidence for microbial growth and activity at -20°C and lower promotes search for microbial life on cryogenic planets, moons and comets (Friedmann and Ocampo-Friedmann 1984; Finegold 1996; Cavicchioli 2002; Jakosky et al. 2003; Marion et al. 2003; Head et al. 2005). These studies could help to develop detection tools with required sensitivity, and identify the most appropriate targets, including organisms able to function in the oxygen-free extraterrestrial environment, e.g., methanogens (Rivkina et al. 2004). Isolation and growth optimization of microorganisms able to subzero growth could unlock access to new types of bio-catalysts efficient at low temperature and low water content for various applications in industry, agriculture and medicine (Feller et al. 1996; Lonhienne et al. 2001; Cavicchioli et al. 2002; Georlette et al. 2004; Marx et al. 2004).
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