Kharchuk M. Features of morphology and functioning of volutin granules of Saccharomyces cerevisiae

The dissertation is devoted to study of vacuolar volutin granules of Saccharomyces cerevisiae. In S.cerevisaie vacuoles in vivo, four morphological types of volutin were observed: diffuse, granule-like membrane-associated, spherical and rod-like. These forms ratio of these forms changed during the growth of culture, as well as under conditions of phosphorus starvation and hypercompensation. The isolated volutin granules were in size from 44 nm to 1.5 μm, were solid and amorphous structures with a smooth and hydrophobic surface. They included inorganic polyphosphates with a chain length of about 55 and 126 phosphate residues, two protein fractions with molecular weights 5-15 and 50-100 kDa, lipids with saturated fatty acids with a chain length of 16 and 18 carbon atoms and metals: K , Mg, Ca, Na and Fe. It is shown that the volutin granules moving (“dancing bodies”) can be of biological nature, since, according to mathematical models of the Wiener and Markov processes, their motion is not typical for classical Brownian particles. This phenomenon is inherent only to living cells, depends on yeast growth stage and physico-chemical factors of environment. It was established that “dancing bodies” has a direct connection with phosphorus metabolism, in particular with polyphosphatase activity. Metachromasy reaction in vitro depends on the quantity and chain length of inorganic polyphosphates, as well as on the ratio of these polymers to calcium ions. Metachromasy reaction of yeast volutin granules was induced in vivo under influence of stress (low temperature, acid stress and anaerobiosis). Metachromasy and “dancing bodies” indexes can be an indicator of the yeast cell response to the stressful effects of environmental factors, including changes in space weather. Interpreting the literature data and the results of our studies, hypothetical models of the genesis of volutin granules, their structure and motion mechanism were proposed.