Candida albicans の Germ Tube 形成過程に関する電子顕微鏡的研究

抄録

The phenomenon of dimorphism exhibited by a number of species of pathogenic fungi has been well known. Candida albicans is one of the dimorphic pathogens which converts the yeast type cell into the germ tube-like filament (germ tube) in invading tissues. In order to study the pathogenicity and the mechanism of Candida albicans infection, the yeast type cells of synchronized growth were innoculated in proline medium to form the germ tubes in vitro, and the initial mechanism of the germ tube formation was investigated by electron microscope using various techniques. The results were as follows : 1. The initial appearance time and the rate of the germ tube formation are closely correlated with the cell size which may reflect cell maturation. The initial appearance in large cells is earlier than small cells and the rate of germ tube formation in the former is higer than in the latter. 2. The thickness of the germ tube wall is about a half of the yeast type cell's. The major part of the germ tube wall consists of the new layer, which is electron less dense, is formed between the inner layer and the cytoplasmic membrane of the mother cell. The electron dense outer layer of the mother cell grows over the germ tube as well, but the inner layer does not continue growing. 3. A great number of intramembranous particles and many invaginations are spreaded over the P. F. surface of the cytoplasmic membrane in freeze etching replica. The invaginations which exist on the germ tube are deformed and fewer than on the yeast type cell. The distribution of the particles becomes sparser toward the tip of the germ tube than that of the yeast type cell. 4. In the tip of the germ tube, the ER-derived vesicles become visible as membrane bounded circles with a diameter of about 100nm, containing some electron less dense granules. 5. With the commencement of germ tube formation, the membranous structures develop quickly, of which the elongating and dividing mitochondria and the lameller ER are found in the cytoplasm. 6. ATPase and acid phosphatase activities are demonstrated in the electron dense vacuoles in the cytochemical methods, which incorporate the phosphorus compounds. 7. As the yeast type cell evaginates, the electron dense vacuoles split and migrate toward the germ tube formation with vesicles, ER and mitochondria. During the development of germ tube, the vacuoles lose their electron density and become the empty structures.