Comparing the rate of growth and metabolic efficiency of yeast experiencing environmental stress or genetic damage.

Physical stresses, toxic substances, and mutations can cause marked decline in the rate of growth (RG). We report that the efficiency of growth (EG), i.e. converting glucose into biomass, responds less profoundly. It remains nearly unaffected for some physical and chemical stresses, but decreases substantially for others, specifically those affecting membrane integrity or ion homeostasis. Mutations (gene deletions) can heavily reduce RG, but much less EG. Moreover, there is no apparent relation between the function of deleted gene and EG. Generally, assays of EG appear as more laborious, less precise, and less informative than those of RG.