The Use of Sodium Azide for Determining the Fermentative Ability of Yeast Developed Under Different Oxygen Tensions.

Since the time of Pasteur quantitative differences in the rate of fermentation or respiration have been reported for yeast developed under different oxygen tensions. Fermentative activity in the majority of cases has been based on rates of C02 production, although to a limited extent rates of glucose utilization and the rates of alcohol formation have also been employed. It should be emphasized that, in the absence of oxygen, an evaluation of C02 produced or of alcohol formed is an index of fermentative activity, whereas the measurement of glucose utilization includes both fermentative and assimilatory processes. In the presence of oxygen, as indicated in studies relating to the Pasteur effect (Lipmann, 1942), fermentative processes tend to be depressed, and, if the medium is suitable, assimilatory processes are enhanced. As will be shown subsequently, identification of the relative fermentative activity of yeast developed under different oxygen tensions is confounded by cell multiplication. New cells formed after inoculation of the test medium obviously cannot be regarded as representative of cells developed under the conditions characteristic of the inoculum.2 Moreover, with cells developed under certain conditions the rate of glucose utilization per cell does not remain constant but diminishes with the length of the observation period. Pickett and Clifton (1941) have indicated that sodium azide in a concentration of 104 M inhibits both the assimilatory and the respiratory processes of yeast. Winzler (1944) has shown that wvith washed bakers' yeast in the presence of 10-O M azide, glucose is metabolized quantitatively to C02, whereas in the absence of azide, assimilatory processes account for a significant portion of the glucose metabolized. From observations made on the inhibition of phosphate uptake in the presence of azide, Spiegelman, Kamen, and Dunn (1946) have suggested that azide interferes with the generation of high-energy phosphate bonds through the oxidative coupling reaction. If this is true, it follows that in the presence of appropriate concentrations of azide fermentative processes should not effect a net increase in high-energy phosphate bonds. Based largely on this explanation for the action of azide and on the observation that the rate of glucose metabolism