Ultraviolet micrography of penetration of exogenous cytochrome c into the yeast cell.

Candida utilis and Saccharomyces cerevisiae in water suspension were found to be very sensitive to exogenous cytochrome c. The protein was taken up by the cells, and the viable count was reduced to a few per cent of the initial value. Micrography at 405 nm revealed penetration of cytochrome c into the interior of the cell. The cytoplasmic membrane lost its capacity to retain intracellular constituents, and ultraviolet-absorbing compounds were released into the medium. When budding cells were subjected to treatment with cytochrome c, the mother cells were found to be more susceptible than the buds. Phosphate buffer protected the cells and spheroplasts against cytochrome c.