LEXEN: Strategies of Long-Term Procaryote Survival in Ancient Permafrost Soils

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This project is designed to investigate the nature of adaptations associated with soil microbes living in polar soils. Viable microorganisms have been recovered from Siberian Arctic permafrost soil samples having survived for 2 - 3 million years, at low temperatures, and low water activity. Recent results suggest that some of these microbes that have survived are capable of biological activity and growth at subzero temperatures and may be active within the frozen permafrost in some instances. Microbial survival would be expected to accommodate even more stringent requirements in Antarctic permafrost: survival for longer periods-up to 10 million years, at lower temperatures, and low water activity. Using archival samples, the investigators will determine whether the microbes in Arctic and Antarctic permafrost are metabolically active in situ. It is hypothesized that unique organisms are selected under three stresses characteristic of the extreme environment of permafrost (severe cold, low water activity, and age) by molecular and physical adaptations. Compatible solutes and gene/protein expression induced by chilling and freezing will be measured for the purpose of elucidating and comparing the adaptive physiologies of microbes from Arctic and Antarctic permafrost. Adaptations will be correlated with freeze tolerance, protection against damage during prolonged frozen storage and metabolic activity at the lower limits of temperature and water activity. Differential scanning calorimetry will be applied as a means of determining whether intracellular microbial solutions remain unfrozen, crystallize, or vitrify under permafrost conditions.