THE RATE OF OXYGEN UTILIZATION BY YEAST AS RELATED TO TEMPERATURE.

Suspensions of the yeast Saccharomyces cerevisiae gave reproducible rates of O(2) uptake over a period of 6 months. The relation of rate of consumption of O(2) to temperature was tested over a wide range of temperatures, and the constant in the formulation of the relationship is found to be reproducible. The values of this constant (micro) have been obtained for five separate series of experiments by three methods of estimation. The variability of micro has the following magnitudes: the average deviation of a single determination expressed as per cent of the mean is +/-2 per cent in the range 30-15 degrees , and +/-0.8 per cent in the range 15-3 degrees C. This constancy of metabolic activity measured as a function of temperature can then be utilized for more precise investigations of processes controlling the velocity of oxidations of substrates, and of respiratory systems controlled by intracellular respiratory pigments. The data plotted according to the Arrhemus equation give average values of the constant micro as follows: for the range 35-30 degrees , micro = 8,290; 30-15 degrees , micro = 12,440 +/-290; 15-3 degrees , micro = 19,530 +/-154. The critical temperatures are at 29.0 degrees and 15.7 degrees C. A close similarity exists between these temperature characteristics (micro) and values in the series usually obtained for respiratory activities in other organisms. This fact supports the view that a common system of processes controls the velocities of physiological activities in yeast and in other organisms.