PRESSURE-STRESS EFFECTS ON THE ULTRASTRUCTURE OF CELLS OF THE DIMORPHIC YEAST CANDIDA-TROPICALIS

The effects of hydrostatic pressure on ultrastructure of the dimorphic yeast Candida tropicalis were investigated by electron microscopy. In yeast form cells, no alterations in the subcellular structure were observed below 100 MPa, but around 200 MPa the subcellular structure was altered, especially in the nucleus and mitochondria. Nuclear membrane pores opened and were disrupted. Mitochondrial cristae were damaged and areas with high electron density were clearly visible in the matrix. In hyphal form cells, the same subcellular structures of nucleus and mitochondria were affected above 200 MPa. Tubular cristae and dense materials were observed in the matrix of mitochondria and their membrane was disrupted. Microbodies in hyphal form cells were also altered by pressure stress; their membrane became irregular and electron-dense materials were observed in the matrix. These drastic changes in nuclear membrane, mitochondria, and microbodies caused by pressure stress resulted in both forms of cells being incapable of growth.