A Metabolic Tradeoff in Wine Saccharomyces cerevisiae: Copper Resistanceand H2S Production

International audience

anglais. Our study examines the ecological and evolutionary implications of excessive hydrogen sulfide (H₂S) production by certain Saccharomyces cerevisiae strains during wine fermentation. H₂S is essential for the synthesis of sulfur-containing amino acids; however, its impact on wine aroma and the high energetic cost of sulfate reduction make its overproduction by some yeast strains particularly intriguing.A comparison between wine yeast strains and wild or velum isolates revealed that wine yeast strains produce more H₂S when exposed to sulfite (SO₂) compared to their wild or velum counterparts. When exploring the potential connection between copper resistance - a trait specific to wine yeast obtained through the amplification of the gene coding for the sulfur-rich protein CUP1p - and sulfur metabolism, we observed that:- A higher copper content in the must correlates with increased H₂S production.- SO₂ in grape must enhances yeast resistance to copper, underscoring the significant role of sulfur flux from the extracellular environment to protein synthesis.- A complex relationship exists between the number of CUP1 gene copies and H₂S production during fermentation, showing an initial positive correlation followed by a negative one. This pattern was replicated using a multicopy plasmid carrying CUP1.Our findings suggest that the extensive use of copper in vineyard management has selected for copper-resistant yeast strains that inadvertently overproduce H₂S. This study highlights the metabolic tradeoff between environmental adaptation and sulfur metabolism. Additionally, the interaction between SO₂ and copper resistance emphasizes the importance of sulfur flux in yeast metabolism. Understanding this tradeoff offers insights into the evolutionary pressures shaping yeast populations and reveals that H₂S production is a complex trait influenced by multiple environmental and genetic factors. This research emphasises the intricate interplay between environmental adaptation and metabolic consequences in yeast, contributing valuable knowledge to both yeast ecology and biotechnological innovation.