Anhydrobiosis in yeast: stabilization by exogenous lactose.

We have found that incubation in lactose solutions (0.75 M) of yeast culture Saccharomyces cerevisiae sensitive to dehydration damage increased the stability of the cells during dehydration. Simultaneously with this increase in viability, a decrease in plasma membrane permeability during rehydration was seen. Using Fourier transform infrared spectroscopy to measure lipid phase transitions, we observed that the lactose treatment depressed the membrane phospholipid phase transition temperature in a sensitive culture of dry yeast. As a result, it leads to the decrease in the damages of molecular organization of membranes during rehydration of dry yeast cells, thus reducing leakage from the cells.

Anhydrobiosis in yeast: activation effect.

Intracellular substances released into the medium during rehydration of dry yeast cells can significantly improve the quality of a synthetic medium. Acceleration of yeast growth in this medium and increased yield of biomass are observed simultaneously. The change in the molecular arrangement of intracellular membranes as a result of the strong dehydration of live organisms is a negative phenomenon that reduces the level of cell viability. However, this phenomenon also represents an adaptive mechanisms which facilitates the maintenance of population viability as a whole under extreme environmental conditions.

[Yeast anhydrobiosis: permeability of the cytoplasmic membrane]. / Angidrobioz drozhzhei pronitsaemost' tsitoplazmaticheskoi membrany.

When studying the dehydration effect of the eukaryotic cells on the structural and functional characteristics of the cytoplasmic membrane, it was established that serious rearrangements of its molecular organization showing up in a drastic increase in the permeability properties occurred in the yeast when the range of residual humidities of the order of 20-30% was reached. These changes were linked to the beginning of losing some bound water by the cells. It was shown that these rearrangements were reparable, and the normal membrane structure could be restored in the process of slow and gradual rehydration of dehydrated cells in the water vapors.

[Influence of plant extracts on the metabolic activity of the yeast Saccharomyces cerevisiae 39]. / Vliianie nekotorykh rastitel'nykh ékstraktov na metabolicheskuiu aktivnost' drozhzhei Saccharomyces cerevisiae 39.

Addition to the nutrient medium of the extracts of camomile, nettle, mint, or Saint-John's-wort to a concentration of 0.5-4% was established to activate the yeast growth. The maximum effect was recorded on the addition of the extracts to the poor "water" medium. The extracts of camomile and Saint-John's-wort were shown to inhibit the alcohol dehydrogenase activity of the yeast cells, whereas the extracts of nettle and mint increased the activity of this enzyme by 62-70%.

[Effect of dehydration of heat-induced restructuring of the cytoplasm membrane of yeast cells]. / Vliianie vysushivaniia na termoindutsirovannye strukturnye perestroiki tsitoplazmaticheskoi membrany kletok drozhzhei.

The effect of dehydration on the cytoplasmic membrane of yeast cells was studied using the method of spin labels. In the course of dehydration, the thermoinduced transition of lipids from the solid to a liquid-crystalline state was found to occur at a higher temperature as compared with native membranes.

[Degradation of ribonucleic acids in yeast cells during desiccation]. / O razrushenii ribonukleinovykh kislot v drozhzhevykh kletkakh pri ikh obezvozhivanii.

From 26 to 43% of RNA undergoes degradation in yeast cells when they pass into the state of anabiosis. Most of the degradation was found to occur at the first stage of cell dehydration when free water was removed from the cells. The mechanism of RNA degradation is supposed to involve enzyme-catalysed processes which are realised in the cell at the early stages of its dehydration.

[Lipid inclusions in cells and their changes during the desiccation and reactivation of yeast organisms]. / Lipidnye vkliucheniia v kletkakh i ikh izmeneniia pri obezvozhivaniia i reaktivatsii drozhzhevykh organizmov.

The formation of lipid granules in Saccharomyces cerevisiae cells was shown to begin in the exponential phase of the culture growth and to be associated with the activity of the endoplasmic reticulum. Lipid granules can be formed (1) when the endoplasmic reticulum cisterns extend and (2) when the endoplasmic reticulum membranes separate relatively small regions of the cell cytoplasm. Yeast cells contain spherosomes which differ in their structure. Lipid granules merge together upon dehydration of yeast cells. The authors discuss possible participation of these granules in the reparation of damages of the intracellular membranes.

[Luminescence microscopy determination of the survival of yeasts after dehydration]. / O liuminestsentno-mikroskopicheskom opredelenii vyzhivaemosti drozhzhevykh organizmov posle obezvozhivaniia.

The technique of luminescent microscopy can be used to determine the survival rate of yeast organisms dehydrated by the convective method. If the cells were subjected to more severe extreme actions, the technique should be combined with the direct microscopy to follow the growth of reactivated organisms and to count the number of microcolonies being formed. The authors propose to classify the state of living organisms after the action of sublethal factors basing on the ability of cells to grow after reactivation.

[Intracellular pool of free amino acids in dehydrated yeast organisms]. / Issledovanie sostoianiia vnutrikletochnogo pula svobodnykh aminokislot pri obezvozhivanii drozhzhevykh organizmov.

The dehydration of Saccharomyces cerevisiae was found to result in a noticeable decrease of the free amino acids content in the cells and in a considerable increase of cytoplasmic membrane permeability for these compounds. When the dehydrated organisms were reactivated, the normal permeability of the cytoplasmic membrane gradually restored and the pool of free amino acids increased in the cells.

[Effect of saccharose and lactose on the resistance of Saccharomyces cerevisiae yeast to desiccation]. / Vliianie sakharozy i laktozy na ustoichivost' drozhzhei Saccharomyces cerevisiae k obezvozhivaniiu.

Incubation of Saccharomyces cerevisiae cells in solutions containing different sucrose or lactose concentrations (0.25 to 1.0 M) makes the organism more resistant to dehydration. The effect is increased when the cells are incubated for longer periods of time. Apparently, certain intracellular reactions making the yeast survive upon dehydration are initiated under these conditions.

[Increased permeability of the intracellular membranes in the dehydration and rehydration of Saccharomyces cerevisiae yeasts]. / O povyshenii pronitsaemosti vnutrikletochnykh membran pri obezvozhivanii-regidratatsii drozhzhei Saccharomyces cerevisiae.

A considerable quantity of potassium and magnesium ions was found to be released from Saccharomyces cerevisiae cells being in the state of anabiosis upon their rehydration. The nearly maximal (for each of the experiments) quantity of ions was released as early as when cells dehydrated to a residual humidity of ca. 20% were rehydrated. A further decrease of the residual humidity down to 8-10% did not increase the leakage of the ions when the cells were rehydrated. It was concluded that the permeability of the cytoplasmic and vacuolar membranes for the ions increased when the cells were dehydrated and that this phenomenon should be attributed to the removal of free water from the cells.

[Cryofractographic study of the structure of yeast cells found in an anabiotic state]. / Kriofraktograficheskoe issledovanie struktury drozhzhevykh kletok, nakhodiashchikhsia v anabioticheskom sostoianii.

Cryofractographic studies of normally growing yeast cells have shown that the length, number and arrangement of slit-like invaginations, as well as the number, frequency of arrangement and dimensions of pores on the nucleolemma, differ among various yeast species. The data on the structure of various organoids published earlier have been confirmed. The volume of all cellular organoids, with an exception of mitochondria, decreases upon dehydration. The invaginations of the plasmalemma coalesce to form a common network. This is important in the course of changes in the volume and density of the cytoplasm of cells in the anabiotic state, maintaining the structural connection of the plasmalemma with the cellular contents, which is necessary for the survival of an organism under extreme conditions.

[Increase in intracellular acid phosphatase activity in dehydrated Saccharomyces cerevisae yeasts]. / Uvelichenie vnutrikletochnoi aktivnosti kisloi fosfatazy pri obezvozhivanii drozhzhei Saccharomyces cerevisiae.

Endocellular acid phosphatase was found to be activated in the course of dehydration of Saccharomyces cerevisiae and at the beginning of its reactivation. This suggests an increase in the number of lysosomes in the cells. Apparently, a damage of the lysosomal membranes may be one of the factors that cause death of yeast cells upon their dehydration.