It has been known that only a very small fraction of the microorganisms present in permafrost sediments can be enumerated by standard methods of plating onto nutrient media. Besides underestimation of the real total number of microorganisms, which is of several orders greater than the number of colony-forming cells, the plating methods provide for no information on the physiological state of microbial cells in situ. Therefore, searching for criteria to distinguish between microbial cells of different physiological state (with emphasis on dormant forms) by direct methods is a very important task. To find such criteria, we characterized the fine structure of dormant cells and their elemental composition by electron microscopy studies (TEM, ESEM, XRMA-SEM) and compared' these characteristics with the bacterial cells in situ. By their specific ultrastructure and peculiarities in the content of biologically important elements, the observed microbial cells in permafrost sediment resembled the experimentally obtained dormant cells.
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