Showing papers by "Michel Aigle published in 2011"
TL;DR: A first comparison of yeast AFs in three synthetic media mimicking the dough/wort/grape must found in baking, brewing, and wine making suggested that human selection targeted the efficiency of cellular reproduction rather than metabolic efficiency.
Abstract: Alcoholic fermentation (AF) conducted by Saccharomyces cerevisiae has been exploited for millennia in three important human food processes: beer and wine production and bread leavening. Most of the efforts to understand and improve AF have been made separately for each process, with strains that are supposedly well adapted. In this work, we propose a first comparison of yeast AFs in three synthetic media mimicking the dough/wort/grape must found in baking, brewing, and wine making. The fermentative behaviors of nine food-processing strains were evaluated in these media, at the cellular, populational, and biotechnological levels. A large variation in the measured traits was observed, with medium effects usually being greater than the strain effects. The results suggest that human selection targeted the ability to complete fermentation for wine strains and trehalose content for beer strains. Apart from these features, the food origin of the strains did not significantly affect AF, suggesting that an improvement program for a specific food processing industry could exploit the variability of strains used in other industries. Glucose utilization was analyzed, revealing plastic but also genetic variation in fermentation products and indicating that artificial selection could be used to modify the production of glycerol, acetate, etc. The major result was that the overall maximum CO(2) production rate (V(max)) was not related to the maximum CO(2) production rate per cell. Instead, a highly significant correlation between V(max) and the maximum population size was observed in all three media, indicating that human selection targeted the efficiency of cellular reproduction rather than metabolic efficiency. This result opens the way to new strategies for yeast improvement.
43 citations
TL;DR: This finding calls into question the extent to which the prion form of Ure2p may be considered an evolutionary adaptation, instead suggesting that an exaptation phenomenon may be more likely than a continuous selection history.
Abstract: We examined aspects of the URE2/[URE3] prion system in Kluyveromyces lactis, which lies on a different evolutionary branch from Saccharomyces. We first analysed the polymorphism of the prion-forming domain in 38 strains. Considerable differences were found between these two genera, with little variation within K. lactis. We then analysed the regulatory function of Ure2p, using a deletion of URE2. We assessed the deregulation of two reporter genes: DAL5 and GDH2. Both were derepressed in the mutant strain, as in Saccharomyces. Finally, we tried to obtain the [URE3] prion from K. lactis. Despite the use of many different experimental conditions, we were unable to obtain a prion from Ure2p. This finding calls into question the extent to which the prion form of Ure2p may be considered an evolutionary adaptation, instead suggesting that an exaptation phenomenon may be more likely than a continuous selection history.
28 citations