Detection of microorganisms in the environment and the preliminary appraisal of their physiological state by X-ray microanalysis

The paper deals with the X-ray microanalysis of the elemental composition of bacteriomorphic particles in 170000-year-old Antarctic permafrost sediments and in indoor dust. A comparative analysis of the phosphorus, sulfur, calcium, and potassium contents and the Ca/K and P/S ratios in these particles and in reference microbial cells occurring in different physiological states showed that the absence of P and/or S peaks in the X-ray spectrum of an object may indicate that it is abiotic. Resting microbial forms can be revealed on the basis of the following characteristic features: an increased content of Ca, a high Ca/K ratio, and a low P/S ratio. Model experiments with nonviable bacterial and yeast micromummies with alterations in the structural and barrier functions of the cytoplasmic membrane showed that micromummies can be recognized by a super-high content of a marker element (e.g., P, K, or Si), accumulated due to facilitated diffusion along a deliberately created concentration gradient. Such an analysis of the permafrost sediment and dust made it possible to suggest the presence of mummified cells in these objects. The possibility of using X-ray microanalysis for the detection of microbial cells in natural habitats in order to enhance the efficiency of ecological monitoring of the environment is discussed.