Yaghnob yeast genomes
The growing interest in the study of Saccharomyces cerevisiae strains from previously unexplored niches is greatly expanding our understanding of this yeast's ecology and evolution. While strains involved in alcoholic fermentation are the most studied, S. cerevisiae has also been isolated from cheese fermentations, suggesting a potential evolutionary specialization of dairy environments. These fermentations are characterized by the predominant presence of lactose, a carbon source that S. cerevisiae cannot metabolize directly but can exploit through the enzymatic activity of co-occurring microorganisms that convert lactose into fermentable substrates such as glucose and galactose. In this study, we analyzed S. cerevisiae strains isolated from an unexplored and remote niche: traditional goat cheese produced by the Yaghnob people, an ethnically and geographically isolated population in Tajikistan. Comparative analyses with published genomes positioned the Yaghnob strains at the base of the phylogenetic dairy clade and revealed distinctive coding sequences and strain-specific single-nucleotide variants present in all Yaghnob strains but absent from the other 1,053 strains analyzed. Further investigation of variants in key genes involved in galactose metabolism provided new insights into the genomic and protein-level evolution of Yaghnob strains, uncovering unique genomic signatures of adaptation to the dairy environment.