Effect of low temperature upon vitality of Saccharomyces cerevisiae phospholipid mutants.

The phospholipid metabolism of Saccharomyces cerevisiae plays a central role in its adaptation to low temperatures. In order to detect the key genes in this adaptation, various phospholipid mutants from the EUROSCARF collection of Saccharomyces cerevisiae BY4742 were tested to ascertain whether the suppression of some genes could improve the fermentation vitality of the cells at low temperature. The cell vitality and phospholipid composition of these mutants were analysed. Some knockouts improved (hmn1Δ) or impaired (cho2Δ and psd1Δ) their vitality at low temperature (13 ° C) but were not affected at optimum temperature (25 ° C). A common trait of the mutants that had some defect in vitality was a lower concentration of phosphatidylcholine and/or phosphatidylethanolamine. The supplementation with choline allowed them to recover viability, probably by synthesis through the Kennedy pathway. Hmn1Δ showed a lower concentration of phosphatidylcholine, which explains the dominant role of the de novo pathway in cellular phosphatidylethanolamine and phosphatidylcholine vs the Kennedy pathway. The absence of such genes as CRD1 or OPI3 produced important changes in phospholipid composition. Cardiolipin was not detected in crd1Δ but phosphatidylglycerol circumvents most of the functions assigned to CL. The considerable reduction in PC diminished the cell vitality of opi3Δ at both temperatures, although the decrease at 13 ° C was more marked.