Morphological changes in the central vacuole ofBlastocystis hominis during in vitro culture

Summary Morphological changes in the central vacuole during the growth in in vitro culture ofBlastocystis hominis were investigated by light and electron microscopy. Most cells in log phase and an early stationary phase showed a positive staining reaction in the central vacuole with PAS or Sudan black B stain, whereas cells in late stationary phase showed few positive reactions. Electron microscopic observations revealed that 95% ofB. hominis cells in log phase and 50% of cells in early stationary phase, had a substantial accumulation of electron-dense material in the central vacuole. In contrast, only 25% of the organisms in late stationary phase had an electron-dense central vacuole, while more than 50% of cells had an electron-lucent central vacuole. These results indicate thatB. hominis accumulated carbohydrates and lipids in the central vacuole during cell growth and that the organism probably consumed these metabolic substances during stationary growth. Therefore, it is strongly suggested that the central vacuole is an important organelle for storage of metabolic substances, such as carbohydrates and lipids, required for cell growth.Abbreviations PBS phosphate-buffered saline - PAS periodic acid-Schiff