[Virus-like particles in yeast protoplasts. I. Electron microscopic demonstration].

In ultrathin sections and negatively stained isolates from protoplasts of a strain of Saccharomyces cerevisiae showing abnormal morphology and degeneration phenomena the presence of virus-like particles within the cells could be demonstrated. The isometric particles have diameters of about 50 nm, the electron dense centre is surrounded by distinct envelope. Protoplastic containing up to 30,000 particles could be found. It could be demonstrated that there exists a correlation between the amount of particles and the degree of degeneration of the cellular substructure. Protoplasts with high titres of virus-like particles obviously undergo lysis. Plaque formation on agar plates could not be seen. It is concluded that the phenomena observed can be compared with cytopathological effects caused by viruses in other cell systems.