Two key groups of organisms are involved in the production of red, white, and sparkling wine. The yeasts, typically strains of Saccharomyces cerevisiae , carry out the primary or alcoholic fermentation, in which sugars are converted to ethanol and CO2. Lactic acid bacteria (LAB), especially

The yeastLachancea thermotolerans(previouslyKluyveromyces thermotolerans) is a species of large, yet underexplored, oenological potential. This study delivers comprehensive oenological phenomes of 94 L. thermotoleransstrains obtained from diverse ecological niches worldwide, classified in nine genetic groups based on their pre-determined microsatellite genotypes. The strains and the genetic groups were compared for their alcoholic fermentation performance, production of primary and secondary metabolites and pH modulation in Chardonnay grape juice fermentations. The common oenological features ofL. thermotoleransstrains were their glucophilic character, relatively extensive fermentation ability, low production of acetic acid and the formation of lactic acid, which significantly affected the pH of the wines. An untargeted analysis of volatile compounds, used for the first time in a population-scale phenotyping of a non-Saccharomycesyeast, revealed that 58 out of 90 volatiles were affected at anL. thermotoleransstrain level. Besides the remarkable extent of intra-specific diversity, our results confirmed the distinct phenotypic performance ofL. thermotoleransgenetic groups. Together, these observations provide further support for the occurrence of domestication events and allopatric differentiation inL. thermotoleranspopulation.

Brettanomyces bruxellensisis a unicellular fungus of increasing industrial and scientific interest over the past 15 years. Previous studies revealed high genotypic diversity amongstB. bruxellensisstrains as well as strain-dependent phenotypic characteristics. Genomic assemblies revealed that some strains harbour triploid genomes and based upon prior genotyping it was inferred that a triploid population was widely dispersed across Australian wine regions. We performed an intraspecific diversity genotypic survey of 1488B. bruxellensisisolates from 29 countries, 5 continents and 9 different fermentation niches. Using microsatellite analysis in combination with different statistical approaches, we demonstrate that the studied population is structured according to ploidy level, substrate of isolation and geographical origin of the strains, underlying the relative importance of each factor. We found that geographical origin has a different contribution to the population structure according to the substrate of origin, suggesting an anthropic influence on the spatial biodiversity of this microorganism of industrial interest. The observed clustering was correlated to variable stress response, as strains from different groups displayed variation in tolerance to the wine preservative sulfur dioxide (SO₂). The potential contribution of the triploid state for adaptation to industrial fermentations and dissemination of the speciesB. bruxellensisis discussed.