SCHIZOSACCHAROMYCES-POMBE IS MORE SENSITIVE TO PRESSURE STRESS THAN SACCHAROMYCES-CEREVISIAE

The effects of hydrostatic pressure on ultrastructure, microtubules an d microfilaments of Schizosaccharomyces pombe were investigated by flu orescence microscopy, conventional electron microscopy and immunoelect ron microscopy. Cells were treated with hydrostatic pressure from 0.1 to 400 MPa for 10 min at room temperature. The nuclear membrane was di srupted at above 100 MPa. At 150 MPa the matrixes of mitochondria had an electron dense area. At 250 MPa the cytoplasmic substances changed dramatically, the cellular organelles could hardly be detected and the fragmented nuclear membrane was barely visible. The fluorescence in a -tubulin was lost in most of the cells at 100 MPa. The gold particles for anti alpha-tubulin were not visible in the cells at the same level . Cell cycle specific actin distribution was lost even at 50 MPa, alth ough actin dots localized at the central region remained unchanged. Th ick actin cables appeared at 100 MPa. Complete depolymerization of F-a ctin was observed at 150 MPa. These results suggest that S. pombe cell s were more sensitive than Saccharomyces cerevisiae cells. The damage to microtubules and nuclear membrane caused by hydrostatic pressure wa s thought to be followed by breakdown of nuclear division apparatus an d the inhibition of nuclear division. This damage might contribute to the frequent formation of polyploidy in S. pombe.