Abstract
Saccharomyces cerevisiae yeast cells may generate energy both by fermentation and aerobic respiration, which are dependent on the type and availability of carbon sources. Cells adapt to changes in nutrient availability, which entails the specific costs and benefits of different types of metabolism but also may cause alteration in redox homeostasis, both by changes in reactive oxygen species (ROS) and in cellular reductant molecules contents. In this study, yeast cells devoid of the SOD1 or SOD2 gene and fermentative or respiratory conditions were used to unravel the connection between the type of metabolism and redox status of cells and also how this affects selected parameters of cellular physiology. The performed analysis provides an argument that the source of ROS depends on the type of metabolism and non-mitochondrial sources are an important pool of ROS in yeast cells, especially under fermentative metabolism. There is a strict interconnection between carbon metabolism and redox status, which in turn has an influence on the physiological efficiency of the cells. Furthermore, pyridine nucleotide cofactors play an important role in these relationships.
Highlights
Carbon metabolism has essential roles in cellular function and in the case of most cells is based on glucose, which is the primary source of energy
It was confirmed in this study that in the yeast cells cultivated in the medium with glycerol the level of adenosine triphosphate (ATP) was very high (Figure 1A) and the mitochondrial network was highly developed (Figure 1B)
The mitochondrial network was well extended in the case of yeast cells cultivated in the medium with 0.5% glucose where energy was produced by both fermentation and respiration (Figure 1B)
Summary
Carbon metabolism has essential roles in cellular function and in the case of most cells is based on glucose, which is the primary source of energy. Saccharomyces cerevisiae yeast cells can utilise glucose, both by fermentation and aerobic respiration. They prefer the less energy efficient fermentative metabolism, even under aerobic conditions, which could be explained by the fact that glucose represses a number of genes that encode key respiratory enzymes [1]. If glucose concentration is very low, or yeast cells grow on non-fermentable carbon sources, respiratory metabolism can be exclusively observed. Cellular redox homeostasis is based on balance between generation and elimination of reactive oxygen species (ROS), which requires the presence of a well-coordinated system including proteins, low molecular weight compounds and pyridine nucleotide cofactors.
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