The Fixation of Carbon Dioxide by Growing and Nongrowing Yeast

Although studies with labeled carbon have revealed that C02 is an active participant in the complex pattern of intermediate metabolism (Werkman and Wood, 1942; Buchanan and Hastings, 1946; Wood, 1946), little information is available concerning the dynamics of C02 metabolism in the living organism. The available evidence indicates that the degree to which C02 is incorporated into the cellular components of an organism depends, among other things, upon whether the organism is resting (nongrowing) or in an active state of protein synthesis (growing). Thus, experiments with rats (Bloom et al., 1947; Schubert and Armstrong, 1949) and mice (Brues and Naranjo, 1949; Skipper et al., 1949) have shown that growing cells tend to fix and retain CO2 carbon to a greater extent than do nongrowing cells. Microorganisms are particularly suitable for a study of this nature since such cells can be grown from almost zero mass to "adult size " under well-defined conditions. In the present investigation, a com-parison is made between the rate of uptake of labeled C02 by yeast cells under-going rapid proliferation in an atmosphere containing labeled C02 and nongrow-