Fermentation Temperature Modulates Phosphatidylethanolamine and Phosphatidylinositol Levels in the Cell Membrane of Saccharomyces cerevisiae

Abstract

During alcoholic fermentation, Saccharomyces cerevisiae is exposed to a host of environmental and physiological stresses. Extremes of fermentation temperature have previously been demonstrated to induce fermentation arrest under growth conditions that would otherwise result in complete sugar utilization at "normal" temperatures and nutrient levels. Fermentations were carried out at 15°C, 25°C, and 35°C in a defined high-sugar medium using three Saccharomyces cerevisiae strains with diverse fermentation characteristics. The lipid composition of these strains was analyzed at two fermentation stages, when ethanol levels were low early in stationary phase and in late stationary phase at high ethanol concentrations. Several lipids exhibited dramatic differences in membrane concentration in a temperature-dependent manner. Principal component analysis (PCA) was used as a tool to elucidate correlations between specific lipid species and fermentation temperature for each yeast strain. Fermentations carried out at 35°C exhibited very high concentrations of several phosphatidylinositol species, whereas at 15°C these yeast strains exhibited higher levels of phosphatidylethanolamine and phosphatidylcholine species with medium-chain fatty acids. Furthermore, membrane concentrations of ergosterol were highest in the yeast strain that experienced stuck fermentations at all three temperatures. Fluorescence anisotropy measurements of yeast cell membrane fluidity during fermentation were carried out using the lipophilic fluorophore diphenylhexatriene. These measurements demonstrate that the changes in the lipid composition of these yeast strains across the range of fermentation temperatures used in this study did not significantly affect cell membrane fluidity. However, the results from this study indicate that fermenting S. cerevisiae modulates its membrane lipid composition in a temperature-dependent manner.

Examining the Role of Membrane Lipid Composition in Determining the Ethanol Tolerance of Saccharomyces cerevisiae

“…Specifically, all of the yeast strains analyzed in this study that experienced fermentation arrest at elevated temperatures had higher concentrations of several phosphatidylinositol species than at other temperatures. Conversely, low-temperature fermentations had the highest concentrations of phosphatidylethanolamine and phosphatidylcholine with medium-chain fatty acids (66). Ergosterol did not appear to have any protective effect, regardless of fermentation temperature, on any of the strains analyzed in this study.…”

Physiological and Transcriptional Responses of Anaerobic Chemostat Cultures of Saccharomyces cerevisiae Subjected to Diurnal Temperature Cycles

“…However, it may have eliminated genes that transcriptionally respond to DTC in glucose-dependent as well as glucose-independent manners. Consistent with temperature-dependent remodeling of membrane composition (16,66,67), transcript levels of genes involved in fatty acid metabolism and, in particular, phospholipid synthesis positively correlated with temperature during DTC (Table 2). Cyclic variations of extracellular The biomass yield during DTC was calculated by using the biomass specific glucose consumption rate listed and a specific growth rate of 0.03 h…”

“…Genes involved in ER-to-Golgi transport were upregulated as the temperature decreased during DTC (Table 2). Since the yeast plasma membrane and cell wall composition are both affected by temperature (66,69), this response may reflect the need for continuous replacement of membrane and cell wall components. Intracellular membrane trafficking is also sensitive to temperature in mammalian cells (70)(71)(72), and in a genomewide screen for sensitivity to high pressure and low temperature, yeast mutants affected in membrane trafficking showed decreased fitness (73).…”

Yeast toxicogenomics: lessons from a eukaryotic cell model and cell factory

“…The plasma membrane lipid composition has also been found to play a role in thermotolerance [59,60 ]. Lipidomic analysis has shown that stuck fermentations (where yeast cells have become dormant) at high temperatures were associated with higher concentrations of several phosphatidylinositol species in the plasma membrane [59], while whole genome sequencing, genome-wide gene expression, and metabolic-flux analyses of yeast strains with improved growth and ethanol production at temperatures above 40 8C revealed a change in sterol composition and increased expression of genes involved in sterol biosynthesis [60 ]. These results suggested that specific substitutions in membrane composition might lead to optimal membrane fluidity in the evolved strains, as seen before in several thermophile species.…”

“…A plasma membrane lipidomic analysis also revealed that the ABC transporter encoding gene PDR18 is involved in the incorporation of ergosterol in the plasma membrane, its expression leading to resistance to the herbicide 2,4-D [57] and growth inhibitory concentrations of ethanol, thus increasing ethanol production in very high gravity fermentations [58]. The plasma membrane lipid composition has also been found to play a role in thermotolerance [59,60 ]. Lipidomic analysis has shown that stuck fermentations (where yeast cells have become dormant) at high temperatures were associated with higher concentrations of several phosphatidylinositol species in the plasma membrane [59], while whole genome sequencing, genome-wide gene expression, and metabolic-flux analyses of yeast strains with improved growth and ethanol production at temperatures above 40 8C revealed a change in sterol composition and increased expression of genes involved in sterol biosynthesis [60 ].…”