Electron microscopic studies on the growth process of fungal cells. I. Nuclear division and accompanying behavior of mitochondria in the genus Candida

Yeast-like cells (blastospores) of Candida albicans and C. stellatoidea present two types of cell wall formation in the process of cell growth. One type occurs in the bud formation, and the other in the germination. The present paper deals with the mechanism of these types of cell wall formation at the electron microscopical level.Bud formation occurred mostly when the yeast-like cells were cultured on Sabouraud's agar medium. The bud wall was produced by extension of the whole layers of the mother cell wall. After the bud cell developed fully in size, as well as in contents, the septal wall was formed in it, first on the mother-cell side and then on the bud-cell side. It was characteristic of electron-dense granules to be seen associated with membranous structures around the newly formed septal wall. These results suggested some possible mechanism for the septal-wall formation.The septal wall may be produced by the accumulation of structural substances activated by the aid of these granules observed, mitochondria, and other membranous structures. It may not be produced by an inward extension of the cell wall, nor by simple fission.The germination of blastospores took place easily with a diversity of unknown environmental factors. After the outer wall ruptured in the germinating region, the inner most layer of the cell wall, which was thin and transparent in electron density, protruded to be thick, so that an intact wall might develop in the daughter cell.In an elongated germ-tube, septal walls were observed. They were similar in appearance to those of mycelial fungi.It is interesting to note that the same type of cells (blastospores) takes a different growth phase depending upon the kind of culture.