Ultrastructural Changes during the Interspecific Protoplast Fusion between Candida tropicalis and Candida boidinii Observed by TEM

抄録

The entire process of the interspecific protoplast fusion between Candida tropicalis and Candida boidinii was observed by transmission electron microscopy(TEM). The protoplasts of the two heterologous strains were fused in medium containing filtersterilized polyethylene glycol, Ca&sup2+; and sorbitol for5to120min. Specimens were taken at appropriate time intervals and prepared for TEM. Protoplasts of the two strains were distinguished by their size as well as by the electron density of the mitochondrial matrix. Changes in the cell membrane of protoplasts were visible immediately after incubation in the fusion medium, and successive changes were noted in the ultrastructure: 1 cell membrane contact between the heterologous protoplasts; 2 waving of the membranes at the site of contact of the protoplasts; 3 flattening of the cell membrane; 4 rupturing and discontinuity of the cell membranes at the site of contact; 5 mixing of cytoplasms of the heterologous protoplasts near the ruptured cell membranes; 6 invisibility of the membranes at the fusion site; 7 nuclear fusion;and 8 completion of the protoplast fusion. These results show that karyogamy and plastogamy occur immediately after incubation of the protoplasts in a fusion medium.