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

该项目旨在调查与生活在极地土壤中的土壤微生物相关的适应的性质。从西伯利亚北极永久冻土样本中发现了活的微生物，这些土壤样本在低温和低水分活度下存活了200-300万年。最近的结果表明，其中一些幸存下来的微生物能够在零度以下的温度下进行生物活性和生长，在某些情况下，可能会在冻结的永久冻土中活动。微生物的生存预计将适应南极永久冻土更严格的要求：在更低的温度和低水活度下生存更长的时间--长达1000万年。利用档案样本，研究人员将确定北极和南极永久冻土中的微生物是否在原地代谢活跃。假设独特的生物是在冻土极端环境(严寒、低水活度和年龄)的三种压力下，通过分子和物理适应而选择出来的。为了阐明和比较北极和南极永久冻土微生物的适应生理，将对低温和冷冻诱导的相容溶质和基因/蛋白质表达进行测量。适应将与耐冻性、在长期冷冻储存期间免受损害以及在温度和水分活度下限下的代谢活动相关。差示扫描量热法将作为一种手段来确定细胞内的微生物溶液在永久冻土条件下是否保持未冻结、结晶或玻璃化。

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.