Abstract
AbstractThe present work aims to elucidate molecular mechanisms underlying hydrogen sulphide production in S. cerevisiae associated to nitrogen deficiency. To assess, at a genome-wide level, how the yeast strain adapted to the progressive nitrogen depletion and to nitrogen re-feeding, gene expression profiles were evaluated during fermentation at different nitrogen concentrations, using the DNA array technology. The results showed that most MET genes displayed higher expression values at the beginning of both control and N-limiting fermentation, just before the time at which the release of sulphide was observed. MET genes were downregulated when yeast stopped growing which could associate MET gene expression levels with cell growth. The over expression of MET genes after nitrogen addition was confirmed by a new release of H2S during the new set of fermentation experiments. In addition, to confirm gene expression profiles observed from macroarray results, real time RT-PCR was performed on 6 genes using additional sets of biological replicates. These genes were selected based on the assumption that differences in sulphide production observed among strains are due to genetic variations of the expression of genes involved in the Sulphate Reduction Pathway. An integration of expression data of genes involved in sulphur assimilation and sulphur amino acid biosynthesis with hydrogen sulphide production is presented.
Highlights
Hydrogen sulphide (H2S) is a secondary metabolite produced by yeasts during alcoholic fermentation, and its amounts largely depends on the yeast strain, media composition and fermentation conditions
The present work intends to establish a relationship between nitrogen availability and H2S liberation with expression levels of genes involved in the Sulphate Reduction Sequence (SRS) pathway
Our ultimate goal is to elucidate molecular mechanisms underlying H2S production in Saccharomyces cerevisiae associated to nitrogen deficiency, in order to minimize its incidence in alcoholic beverage production
Summary
Hydrogen sulphide (H2S) is a secondary metabolite produced by yeasts during alcoholic fermentation, and its amounts largely depends on the yeast strain, media composition and fermentation conditions. In Saccharomyces cerevisiae, sulphide is the product of the Sulphate Reduction Sequence (SRS) pathway and acts as an intermediate in the biosynthesis of sulphur-containing amino acids. The biosynthesis of sulphur amino acids requires nitrogen-containing carbon precursors derived from the intracellular nitrogen pool and sulphide from the sulphate reduction pathway
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