T W O FIGURES
I n a previous, general account of carbohydrate and lipid anabolism in bakers' yeast, Stier ( '39) reported a prelimiiiary series of experiments describing the course of polysaccharide accumulation in starved and fresh commercial bakers ' yeast metabolizing dextrose under nonproliferating conditions at 25Β°C. It was found that starved cells assimilated 60-70% less total carbohydrate in the presence of oxygen than in its absence, whereas "fresh" yeast synthesized only 1 0 3 0 % less under aerobic conditions. The maximum amount of carbohydrate stored in fresh yeast and in dissimilated (starved) yeast under anaerobic conditions was, however, approximately the same.
I n the experiments reported in this paper we studied the timecourse of both glycogen a3d total carbohydrate assimilation at a much lower temperature (5Β°C.) in order to follow the course of the assimilation reaction in greater detail than heretofore. The time-courses of dextrose utilization and alcohol accumulation were also followed simultaneously. Our primary aim in these experiments was to make a survey of the general course of these various processes in order to formulate experimental conditions for a standard assimilation reaction to be used subsequently in a kinetic attack on the in vivo mechanism of assimilation.
EXPERIMENTAL A pure strain of commercial bakers' yeast-GM yeast type No. 139 from Standard Brands 1nc.-was employed in these experiments. It was shipped directly from the factory under refrigeration and was received in our laboratory within 24 hours. Since the carbohydrate content of-yeast decreases after separation of the cells from their culture medium (see Stier and Stannard, '36) it was thought advisable to reduce the carbohydrate stores to a minimum by a starvation treatment before using the cells in our assimilation experiments.
Support from the William F. Milton Fund of Harvard University is gratefully acknowledged.