Dependency of size of Saccharomyces cerevisiae cells on growth rate

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Abstract
The mean size and percentage of budded cells of a wild-type haploid strain of S. cerevisiae grown in batch culture over a wide range of doubling times (.tau.) were measured using microscopic measurements and a particle size analyzer. Mean size increased over a 2.5-fold range with increasing growth rate (from .tau. = 450 min to .tau. = 75 min). Mean size is principally a function of growth rate and not of a particular C source. The duration of the budded phase increased at slow growth rates according to the empirical equation, budded phase = 0.5.tau. + 27 (all in min). Using a recent model of the cell cycle where division is thought to be asymmetric, equations were derived for mean cell age and mean cell volume. The data are consistent with the notion that initiation of the cell cycle occurs at start after attainment of a critical cell size and this size is dependent on growth rate, being, at slow growth rates, 63% of the volume of fast growth rates. Previous reports are reanalyzed in the light of the unequal division model and associated population equations.