Under natural conditions yeast cells as well as other microorganisms are regularly subjected to t... more Under natural conditions yeast cells as well as other microorganisms are regularly subjected to the influence of severe drought, which leads to their serious dehydration. The dry seasons are then changed by rains and there is a restoration of normal water potential inside the cells. To survive such seasonal changes a lot of vegetative microbial cells, which belong to various genera and species, may be able to enter into a state of anhydrobiosis, in which their metabolism is temporarily and reversibly suspended or delayed. This evolutionarily developed adaptation to extreme conditions of the environment is widely used for practical goals - for conservation of microorganisms in collections, for maintenance and long storage of different important strain-producers and for other various biotechnological purposes. This current review presents the most important data obtained mainly in the studies of the structural and functional changes in yeast cells during dehydration. It describes the changes of the main organelles of eukaryotic cells and their role in cell survival in a dry state. The review provides information regarding the role of water in the structure and functions of biological macromolecules and membranes. Some important intracellular protective reactions of eukaryotic organisms, which were revealed in these studies and may have more general importance, are also discussed. The results of the studies of yeast anhydrobiosis summarized in the review show the possibilities of improving the conservation and long-term storage of various microorganisms and of increasing the quality of industrially produced dry microbial preparations.
Ascospores of Talaromyces.macrosporus belong to the most stress resistant eukaryotic cells and sh... more Ascospores of Talaromyces.macrosporus belong to the most stress resistant eukaryotic cells and show a constitutive dormancy, i.e., no germination occurs in the presence of rich growth medium. Only an extreme trigger as very high temperature or pressure is able to evoke synchronized germination. In this study, several changes within the thick cell wall of these cells are observed after a heat treatment: (i.) a change in its structure as shown with EPR and X-ray diffraction; (ii.) a release of an abundant protein into the supernatant, which is proportional to the extent of heat activation; (iii.) a change in the permeability of the cell wall as judged by fluorescence studies in which staining of the interior of the cell wall correlates with germination of individual ascospores. The gene encoding the protein, dubbed ICARUS, was studied in detail and was expressed under growth conditions that showed intense ascomata (fruit body) and ascospore formation. It encodes a small 7–14 kD protei...
Lannea microcarpa, a multipurpose tree species from the dry African savanna, sheds seeds that oft... more Lannea microcarpa, a multipurpose tree species from the dry African savanna, sheds seeds that often display inhibition of germination. The underlying mechanism was investigated using seeds processed from fully matured fruits collected from natural stands in Burkina Faso. Germination of fresh seeds was variable (16¿28%), while they did not germinate after drying and rehydration. Mechanical scarification of the endocarp at
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1994
Dried and hydrated embryos of wheat seeds (viable and nonviable, harvested in 1992 and 1976, resp... more Dried and hydrated embryos of wheat seeds (viable and nonviable, harvested in 1992 and 1976, respectively) were studied by the EPR method with the use of the spin-labeling technique. Spin label Tempone was used for testing the plasmalemma integrity. It has been demonstrated that the loss of seed viability correlates with the loss of external membrane integrity. Spin-labeled derivatives of stearic acids, 5-doxylstearate I(12.3) and 16-doxylstearate I(1.14), were used to monitor the changes in structural characteristics of embryo cell membranes. The EPR spectra of these spin labels represent the superpositions of at least two signals from the molecules located in domains characterized by different fluidity. The comparison of the EPR spectra from I(12.3) in embryo cells and model systems (total fraction of lipids and purified seed oil) indicates that the majority of spin label molecules is located in the lipid surroundings, while the minor portion of I(12.3) is localized in so-called lipid bodies which contain seed oil. The embryo cells of viable and nonviable seeds differ in the sizes of these 'solid' and 'fluid' intracellular domains. The environment of spin label molecules located in cell membranes of nonviable seeds is more rigid, as compared with that in the membranes of the viable cells. The study of dehydration-rehydration effects has demonstrated that the loss of water causes the restriction of spin label mobility in embryo cells from both kinds of seeds.
We discuss current ideas of how membranes in desiccation-tolerant plant organ(ism)s are protected... more We discuss current ideas of how membranes in desiccation-tolerant plant organ(ism)s are protected from the deleterious effect of complete water removal. Results of studies with model membranes showed that sugars play a major role in preventing fusion, phase transitions and most ...
Because water is essential in the formation and maintenance of the bilayer structure, dehydration... more Because water is essential in the formation and maintenance of the bilayer structure, dehydration has a major impact on the conformation of membranes. Dehydration leads to increases in the gel-to-liquid crystalline transition temperature (Tm) and, depending on the phospholipid species involved, to the formation of nonbilayer phases. Di-and oligosaccharides, which are abundant in desiccation-tolerant organisms, are particularly effective at suppressing the dehydration-induced increase in Tm, by interacting with the polar headgroups. Moreover, they prevent membrane fusion by the timely formation of a glassy matrix. Both properties are crucial in the protection of liposomes from dehydration stress. Dry, desiccation-tolerant organisms lack non-bilayer phases, but gel phase has been encountered. Tm, of membranes in dried organisms is lower than that of dried isolated membranes, probably as a result of the interaction of the sugars with the headgroups and the partitioning of amphiphilic (...
Under natural conditions yeast cells as well as other microorganisms are regularly subjected to t... more Under natural conditions yeast cells as well as other microorganisms are regularly subjected to the influence of severe drought, which leads to their serious dehydration. The dry seasons are then changed by rains and there is a restoration of normal water potential inside the cells. To survive such seasonal changes a lot of vegetative microbial cells, which belong to various genera and species, may be able to enter into a state of anhydrobiosis, in which their metabolism is temporarily and reversibly suspended or delayed. This evolutionarily developed adaptation to extreme conditions of the environment is widely used for practical goals - for conservation of microorganisms in collections, for maintenance and long storage of different important strain-producers and for other various biotechnological purposes. This current review presents the most important data obtained mainly in the studies of the structural and functional changes in yeast cells during dehydration. It describes the changes of the main organelles of eukaryotic cells and their role in cell survival in a dry state. The review provides information regarding the role of water in the structure and functions of biological macromolecules and membranes. Some important intracellular protective reactions of eukaryotic organisms, which were revealed in these studies and may have more general importance, are also discussed. The results of the studies of yeast anhydrobiosis summarized in the review show the possibilities of improving the conservation and long-term storage of various microorganisms and of increasing the quality of industrially produced dry microbial preparations.
Ascospores of Talaromyces.macrosporus belong to the most stress resistant eukaryotic cells and sh... more Ascospores of Talaromyces.macrosporus belong to the most stress resistant eukaryotic cells and show a constitutive dormancy, i.e., no germination occurs in the presence of rich growth medium. Only an extreme trigger as very high temperature or pressure is able to evoke synchronized germination. In this study, several changes within the thick cell wall of these cells are observed after a heat treatment: (i.) a change in its structure as shown with EPR and X-ray diffraction; (ii.) a release of an abundant protein into the supernatant, which is proportional to the extent of heat activation; (iii.) a change in the permeability of the cell wall as judged by fluorescence studies in which staining of the interior of the cell wall correlates with germination of individual ascospores. The gene encoding the protein, dubbed ICARUS, was studied in detail and was expressed under growth conditions that showed intense ascomata (fruit body) and ascospore formation. It encodes a small 7–14 kD protei...
Lannea microcarpa, a multipurpose tree species from the dry African savanna, sheds seeds that oft... more Lannea microcarpa, a multipurpose tree species from the dry African savanna, sheds seeds that often display inhibition of germination. The underlying mechanism was investigated using seeds processed from fully matured fruits collected from natural stands in Burkina Faso. Germination of fresh seeds was variable (16¿28%), while they did not germinate after drying and rehydration. Mechanical scarification of the endocarp at
Biochimica et Biophysica Acta (BBA) - Biomembranes, 1994
Dried and hydrated embryos of wheat seeds (viable and nonviable, harvested in 1992 and 1976, resp... more Dried and hydrated embryos of wheat seeds (viable and nonviable, harvested in 1992 and 1976, respectively) were studied by the EPR method with the use of the spin-labeling technique. Spin label Tempone was used for testing the plasmalemma integrity. It has been demonstrated that the loss of seed viability correlates with the loss of external membrane integrity. Spin-labeled derivatives of stearic acids, 5-doxylstearate I(12.3) and 16-doxylstearate I(1.14), were used to monitor the changes in structural characteristics of embryo cell membranes. The EPR spectra of these spin labels represent the superpositions of at least two signals from the molecules located in domains characterized by different fluidity. The comparison of the EPR spectra from I(12.3) in embryo cells and model systems (total fraction of lipids and purified seed oil) indicates that the majority of spin label molecules is located in the lipid surroundings, while the minor portion of I(12.3) is localized in so-called lipid bodies which contain seed oil. The embryo cells of viable and nonviable seeds differ in the sizes of these 'solid' and 'fluid' intracellular domains. The environment of spin label molecules located in cell membranes of nonviable seeds is more rigid, as compared with that in the membranes of the viable cells. The study of dehydration-rehydration effects has demonstrated that the loss of water causes the restriction of spin label mobility in embryo cells from both kinds of seeds.
We discuss current ideas of how membranes in desiccation-tolerant plant organ(ism)s are protected... more We discuss current ideas of how membranes in desiccation-tolerant plant organ(ism)s are protected from the deleterious effect of complete water removal. Results of studies with model membranes showed that sugars play a major role in preventing fusion, phase transitions and most ...
Because water is essential in the formation and maintenance of the bilayer structure, dehydration... more Because water is essential in the formation and maintenance of the bilayer structure, dehydration has a major impact on the conformation of membranes. Dehydration leads to increases in the gel-to-liquid crystalline transition temperature (Tm) and, depending on the phospholipid species involved, to the formation of nonbilayer phases. Di-and oligosaccharides, which are abundant in desiccation-tolerant organisms, are particularly effective at suppressing the dehydration-induced increase in Tm, by interacting with the polar headgroups. Moreover, they prevent membrane fusion by the timely formation of a glassy matrix. Both properties are crucial in the protection of liposomes from dehydration stress. Dry, desiccation-tolerant organisms lack non-bilayer phases, but gel phase has been encountered. Tm, of membranes in dried organisms is lower than that of dried isolated membranes, probably as a result of the interaction of the sugars with the headgroups and the partitioning of amphiphilic (...
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