Saccharomyces paradoxus

Ecology

Saccharomyces paradoxus is mostly isolated from deciduous trees (oak, maple, birch), and in some rare occasions on insects and fruits. It is often found in sympatry with other Saccharomyces species. 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.

Biogeography

Unlike most other Saccharomyces species, there is no evidence that Saccharomyces paradoxus has been domesticated by humans. Accordingly, its biogeography is mostly marked by natural processes like limited migration, A fifth population is represented by a singleton isolate from Hawaii. Two isolates from South America, described as Saccharomyces cariocanus, are genetically indistinguishable but exhibit post-zygotic isolation when crossed to strains from the American population, due to chromosomal translocations.

Reproduction

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. This purges recessive deleterious mutations that accumulated during clonal expansion, in a process known as "genome renewal". 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.

Like in other Saccharomyces species, heterothallism can be restored using standard genetic tools, to obtain stable haploid strains for experimental purposes.

References

References

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15. (2008). "Population genomics of the wild yeast Saccharomyces paradoxus: Quantifying the life cycle". Proceedings of the National Academy of Sciences of the United States of America.
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