Transient Responses of Saccharomyces uvarum to a Change of the Growth-limiting Nutrient in Continuous Culture

Department of Biotechnology, Swiss Federal Institute of Technology, Hoenggerberg, CH-8093 Zürich, Switzerland ABSTRACT SUMMARY: The transition of Saccharomyces uvarum from oxidative to oxido-reductive glucose metabolism was characterized by the immediate formation of ethanol and the gradual adaptation of cells to a new physiological state, as expressed by a decrease in mitochondrial cytochrome content and a loss of malate dehydrogenase activity. Shifting the cells from carbon-limited to oxygen-, nitrogen- and iron-limited media in a continuous culture growing oxidatively led to the initiation of the same effects. The results lend support to the concept of a limited respiratory capacity as the basis for the occurrence of oxido-reductive glucose metabolism. Limitation of growth by a nutrient other than glucose results in an imbalance between glucose flux and biosynthetic potential of the cells and causes oxido-reductive glucose breakdown.