Exploring the northern limit of the distribution of S accharomyces cerevisiae and S accharomyces paradoxus in N orth A merica

We examined the northern limit of S accharomyces cerevisiae and S accharomyces paradoxus in northeast A merica. We collected 876 natural samples at 29 sites and applied enrichment methods for the isolation of mesophilic yeasts. We uncovered a large diversity of yeasts, in some cases, associated with specific substrates. Sequencing of the ITS 1, 5.8S and ITS 2 loci allowed to assign 226 yeast strains at the species level, including 41 S . paradoxus strains. Our intensive sampling suggests that if present, S . cerevisiae is rare at these northern latitudes. Our sampling efforts spread across several months of the year revealed that successful sampling increases throughout the summer and diminishes significantly at the beginning of the fall. The data obtained on the ecological context of yeasts corroborate what was previously reported on P ichiaceae , S accharomycodaceae , D ebaryomycetaceae and P haffomycetaceae yeast families. We identified 24 yeast isolates that could not be assigned to any known species and that may be of taxonomic, medical, or biotechnological importance. Our study reports new data on the taxonomic diversity of yeasts and new resources for studying the evolution and ecology of S . paradoxus .