Preservation of cell structures in permafrost: a model for exobiology.

The present report is the first contribution toward a comprehensive fine-structural study of microbial cells from permafrost. Prokaryotes with a variety of cell wall types demonstrate high stability of cell structure after long-term cryopreservation in frozen soils and sediments of the Arctic. The surface capsular layers that were a salient feature of the cells both in situ and on nutrient media may be an adaptation to low temperature. To the extent that permafrost regions on Earth approximate Martian conditions, preservation of cell structure there can serve as the basis for predictions about preservation in Martian permafrost sediments.