EFFECTS OF HYDROSTATIC-PRESSURE ON THE ULTRASTRUCTURE AND LEAKAGE OF INTERNAL SUBSTANCES IN THE YEAST SACCHAROMYCES-CEREVISIAE

The structural damage to and leakage of internal substances from Saccharomyces cerevisiae 0-39 cells induced by hydrostatic pressure were investigated. By scanning electron microscopy, yeast cells treated at room temperature with pressures below 400 MPa for 10 min showed a slight alteration in outer shape. Transmission electron microscopy, however, showed that the inner structure of the cell began to be affected, especially the nuclear membrane, when treated with hydrostatic pressure around 100 MPa at room temperature for 10 min; at more than 400-600 MPa, further alterations appeared in the mitochondria and cytoplasm. Furthermore, when high pressure treatment was carried out at -20-degrees-C, the inner structure of the cells was severely damaged even at 200 MPa, and almost all of the nuclear membrane disappeared, although the fluorescent nucleus in the cytoplasm was visible by 4,6-diamidino-2-phenylindole (DAPI) staining. The structural damage of pressure-treated cells was accompanied by the leakage of internal substances. The efflux of UV-absorbing substances including amino acid pools, peptides, and metal ions increased with increase in pressure up to 600 MPa. In particular, amounts of individual metal ion release varied with the magnitude of hydrostatic pressures over 300 MPa, which suggests that the ions can be removed from the yeast cells separately by hydrostatic pressure treatment.