THE FIXATION OF CARBON DIOXIDE BY GROWING AND NONGROWING YEAST

Abstract
Yeasts were cultured in closed systems containing isotopic carbon dioxide (C14O2) in order to determine the percentage of total C (in that fraction that had been acid-washed and ether-extracted) originating from the CO2 in the air. Growing yeast cells rapidly fixed CO2 ob-taining as much as 5% of their total C from the air. After an exposure of 10 days under the same CO2 tension, nongrowing cells contained only 1% C derived from the atmosphere. At low concns. of CO2, the uptake of this C by growing yeast is proportional to the CO2 concn. When the CO2 concn. exceeds 5%, the % of the total C represented by fixed C becomes essentially constant.