Incubation of yeast cells for 21 hours in solutions of certain sugars and polyols produces cells capable of forming CO2 from glucose at a high rate and without an initial lag as compared to cells starved by incubation in water. Other sugars and other compounds, including amino acids, purines and pyrimidines, and organic and inorganic salts, were ineffective o r reduced C 0 2 production. Readily metabolized sugars were effective at concentrations of 0.001 M , poorly metabolized sugars required higher concentration, and non-metabolized sugars were ineffective. However, mannitol and sorbitol, non-metabolized polyols structurally related to utilized sugars, were effective. Alcohols and polyols added to the cells after incubation in water overcame the lag period. Sugars produced a persistent change, acted faster than polyols, and were more effective in the presence of non-effective compounds. Readily utilized sugars a t high concentrations reduced cell viability and the decarboxylase-and C02-producing capacities of cell extracts. The nicotinamide adenine dinucleotide contents of extracts did not indicate deficiencies, and differences in adenosine triphosphate contents appeared not to be significant. The data may be interpreted as evidence for an effect by the sugars and polyols primarily upon intracellular membranes.We have noted, in studies with X-irradiated yeast, that cells incubated in solutions of certain sugars or hexitols have a greater capacity to produce C 0 2 than cells starved by incubation in water (12,14). The rate of C 0 2 production is increased and the lag in output characteristic of starved cells does not occur. Starvation of exponential phase cells normally reduces their capacity to use oxygen and to produce C 0 2 (17). Though the activity of glycolytic erlzymes appears to be unaffected (1 5), various changes may occur in yeast cells during starvation, includirig a depletion or rearrangement of carbohydrate reserves (1) and turnover of proteins and nucleic acids (8). Even in this complex situation it seemed possible that an altered capacity to produce C02, a reasonably specific effect, could serve as a key to study the mechanisms by which sugars and hexitols influence these cells.In the studies reported below, only sugars and sugar alcohols (polyols), among many compounds included during incubation, enhanced C 0 2 production. A structural specificity, related to sugar usability, appears to be necessary for effectiveness. The action of alkyl alcohols in eliminating the lag period suggests that a change in the internal membranes of the yeast cells may be involved in the altered C 0 2 response.
Materials and MethodsYeast cells (Saccharomyces cere~~isiae, originally isolated from a cake of Fleishmanns bakers' yeast) were grown and handled as previously described (12,17). Exponential phasecells were harvested and washed twice with distilled water by centrifugation. The cells were resuspended at double their final growth concentration (4 X 107 cells/ml in all cases, to avoid a possible difference in respon...