Reproductive capacity and mode of death of yeast cells

The technique of micromanipulation was used to observe the number of daughter cells produced by individual cells of two yeasts, one a brewing strain and the other a hexaploid hybrid. The mode in which these cells died was also recorded. An average reproductive capacity of 34 daughter cells was found for the brewing yeast and of 17 daughter cells for the hexaploid strain. Two distinct modes of death were observed, one in which the final daughter cell appeared normal and the other where the last daughter cell could not be detached from its mother and both cells died. A correlation was obtained between the mode of death of a cell and its reproductive capacity. A number of final daughter cells (the 28th - 46th buds of their mother cell) was also observed through a considerable number of divisions and these cells were found apparently normal in their reproductive ability. It is suggested that cessation of budding is a consequence of reduction of the active surface to volume ratio because of the lower metabolic activity of scar tissue.