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Category: Applied and Industrial Microbiology
Saccharomyces cerevisiae Response to High Hydrostatic Pressure, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815646/9781555814236_Chap08-1.gif /docserver/preview/fulltext/10.1128/9781555815646/9781555814236_Chap08-2.gifAbstract:
Life is within a Euclidean space (with the usual Euclidean metric), as there are only three essential axes for sustaining life. The first is the source of energy, the second is water, and the third is a range of conditions that the organism can tolerate, meaning how much of a stress an organism can cope with. The major source for energy and carbon in the yeast Saccharomyces cerevisiae is glucose, and glycolysis is the general pathway for conversion of glucose to pyruvate. This chapter describes the effects of short exposures of S. cerevisiae to lethal and sublethal pressures, with a focus on cellular inactivation/resistance and stress response, respectively. High hydrostatic pressure (HHP) exerts a broad effect within eukaryotic cells, with characteristics similar to common stresses, such as temperature, ethanol, and oxidative stresses. Yeast cells in stationary phase, which undergo growth arrest and a variety of morphological and physiological changes, are more resistant to pressure than proliferating cells. Application of HHP in the food processing industry has stimulated the effort to understand the impact of pressure in combination with other parameters, such as high or low temperature, on cell viability. Hydrostatic pressure also interferes with cellular membrane structure, increasing the order of lipid molecules, especially in the vicinity of proteins. The heat shock response in S. cerevisiae is one of the best-studied pathways of eukaryotic cells, and pretreatment with a mild heat stress leads to protection against more severe heat shock and several other stresses, including HHP.
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Effect of HHP on different wild-type yeast cells. Cells from logarithmic phase were submitted to various hydrostatic pressures for 30 min each time. Cell survival is expressed as percentage of viable cells. The standard deviations are smaller than the symbols used.
Transmission electron micrographs of a thin section through Saccharomyces cerevisiae Y440 wild-type cells. (a and b) Typical S. cerevisiae cell at atmospheric pressure. (b) Detailed image illustrating the appearance of the cell wall, cell membrane, and Golgi apparatus. (c and d) Cell submitted to 200 MPa for 30 min. The cell outer shape was almost unaffected. The arrow points to a broken nuclear membrane. (d) Detail of the cell membrane. (e and f) Heat shock-pretreated cell (40°C for 60 min) submitted to HHP of 200 MPa. (f) Detailed image showing a lamellar structure flanking the cell membrane. CM, cell membrane; CW, cell wall; NM, nuclear membrane; N, nucleus; V, vacuoles; M, mitochondria; G, Golgi apparatus; ER, endoplasmic reticulum. The bar in panel a represents 0.8 µm; the bars in panels b, d, and f represent 0.3 µm; and the bars in panels c and e represent 0.5 µm. Reprinted from Letters in Applied Microbiology ( 24 ) with permission of the publisher.
Fluorescent micrographs of Saccharomyces cerevisiae cells stained for F-actin with rhodamine-conjugated phalloidin. (a) Untreated cells evidencing the cell cycle-specific organization of microfilaments; (b to f) cells treated with 100 (b), 150 (c), 200 (d), 250 (e), and 300 (f) MPa. Reprinted from High Pressure Bioscience and Biotechnology ( 42 ) with permission of the publisher.
Global gene expression profile in functional categories. Black bars and white bars represent the percentages of induced and repressed genes, respectively. The classification is based on the MIPS database, available on the web. Reprinted from FEBS Letters ( 23 ) with permission of the publisher.
Up-regulated characterized genes after 30 min of HHP (200 MPa) a