Saccharomyces paradoxus | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Fungi |
Division: | Ascomycota |
Class: | Saccharomycetes |
Order: | Saccharomycetales |
Family: | Saccharomycetaceae |
Genus: | Saccharomyces |
Species: | S. paradoxus
|
Binomial name | |
Saccharomyces paradoxus Bach.-Raich., 1914
|
Saccharomyces paradoxus is a wild yeast and the closest known species to the baker's yeast Saccharomyces cerevisiae. It is used in population genomics and phylogenetic studies to compare its wild characteristics to laboratory yeasts.[1]
Saccharomyces paradoxus is mostly isolated from deciduous trees (oak, maple, birch), and in some rare occasions on insects and fruits.[2][3][4][5] It is often found in sympatry with other Saccharomyces species.[6][7][8] Like Saccharomyces cerevisiae, it has a worldwide distribution and it is mesophilic, which limits its natural distribution to low latitudes. However, Saccharomyces paradoxus typically grows at lower temperatures than Saccharomyces cerevisiae, resulting in a slight shift in its distribution toward cooler regions, like British islands and Eastern Canada.[2][8][9]
Unlike most other Saccharomyces species, there is no evidence that Saccharomyces paradoxus has been domesticated by humans.[3][11] Accordingly, its biogeography is mostly marked by natural processes like limited migration,[3] glacial refugia[12] and adaptation to climate.[10] At least four genetically and phenotypically distinct populations of Saccharomyces paradoxus have been identified, corresponding to main geographical divisions: Europe (including West Siberia), Far East Asia (Japan, Eastern Siberia), North America (North American East and West coasts, Great Lakes region) and North-East America (Gaspé Peninsula, Saint Lawrence Valley and Appalaches), respectively.[3][9][10][11] Representative strains of these populations exhibit partial post-zygotic isolation.[12][13] A fifth population is represented by a singleton isolate from Hawaii.[3][11] Some strains from the European population are found in North America and New Zealand and likely result from recent colonization events.[14][15] Two isolates from South America, described as Saccharomyces cariocanus,[16] are genetically indistinguishable but exhibit post-zygotic isolation when crossed to strains from the American population, due to chromosomal translocations.[13]
Saccharomyces paradoxus is naturally homothallic, and is mostly found as diploid in the environment. Reproduction is mostly clonal and 99% of sexual reproduction occurs between spores from the same ascus.[17] This purges recessive deleterious mutations that accumulated during clonal expansion, in a process known as "genome renewal".[18][19] Post-zygotic isolation between strains of Saccharomyces paradoxus is commonly observed and could be either due to genetic divergence between populations or to chromosomal changes within populations.[12][13]
Like in other Saccharomyces species, heterothallism can be restored using standard genetic tools, to obtain stable haploid strains for experimental purposes.