''Saccharomyces paradoxus'' is a wild

yeast Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom (biology), kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are est ...

and the closest known species to the baker's yeast ''

Saccharomyces cerevisiae ''Saccharomyces cerevisiae'' () (brewer's yeast or baker's yeast) is a species of yeast (single-celled fungal microorganisms). The species has been instrumental in winemaking, baking, and brewing since ancient times. It is believed to have be ...

''. It is used in

population genomics Population genomics is the large-scale comparison of DNA sequences of populations. Population genomics is a neologism that is associated with population genetics. Population genomics studies genome-wide effects to improve our understanding of micro ...

and

phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...

studies to compare its wild characteristics to laboratory yeasts.

Ecology

''Saccharomyces paradoxus'' is mostly isolated from

deciduous In the fields of horticulture and botany, the term deciduous () means "falling off at maturity" and "tending to fall off", in reference to trees and shrubs that seasonally shed Leaf, leaves, usually in the autumn; to the shedding of petals, aft ...

trees (oak, maple, birch), and in some rare occasions on insects and fruits. It is often found in

sympatry In biology, two closely related species or populations are considered sympatric when they exist in the same geographic area and thus frequently encounter each other. An initially interbreeding population that splits into two or more distinct spe ...

with other ''

Saccharomyces ''Saccharomyces'' is a genus of fungi that includes many species of yeasts. ''Saccharomyces'' is from Greek σάκχαρον (sugar) and μύκης (fungus) and means ''sugar fungus''. Many members of this genus are considered very important in f ...

'' species. Like ''Saccharomyces cerevisiae'', it has a worldwide distribution and it is

mesophilic A mesophile is an organism that grows best in moderate temperature, neither too hot nor too cold, with an optimum growth range from . The optimum growth temperature for these organisms is 37 °C (about 99 °F). The term is mainly applied ...

, 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

Saccharomyces paradoxus worldwide distribution

Unlike most other ''

'' 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, glacial refugia and adaptation to climate. 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. Representative strains of these populations exhibit partial post-zygotic isolation. A fifth population is represented by a singleton isolate from Hawaii. Some strains from the European population are found in North America and New Zealand and likely result from recent colonization events. 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 translocation In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes "balanced" and "unbalanced" translocation, with three main types: "reciprocal", "nonreciprocal" and "Robertsonian" transloc ...

Reproduction

''Saccharomyces paradoxus'' is naturally

homothallic In fungi and algae, homothallism refers to the condition in which a single individual or thallus carries the genetic determinants (i.e., both mating types or sexes) required to undergo sexual reproduction without the need for a distinct mating partn ...

, and is mostly found as

diploid Ploidy () is the number of complete sets of chromosomes in a cell, and hence the number of possible alleles for autosomal and pseudoautosomal genes. Here ''sets of chromosomes'' refers to the number of maternal and paternal chromosome copies, ...

in the environment. Reproduction is mostly clonal and 99% of

sexual reproduction Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete ( haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote tha ...

occurs between spores from the same

ascus An ascus (; : asci) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some gen ...

. This

purges In history, religion and political science, a purge is a position removal or execution of people who are considered undesirable by those in power from a government, another, their team leaders, or society as a whole. A group undertaking such an ...

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 Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes ( mutations) through time, often leading to reproductive isolation and continued mutation even after the populations h ...

between populations or to chromosomal changes within populations. Like in other ''

'' species,

heterothallism Heterothallic species have sexes that reside in different individuals. The term is applied particularly to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable ...

can be restored using standard genetic tools, to obtain stable

haploid Ploidy () is the number of complete sets of chromosomes in a cell (biology), cell, and hence the number of possible alleles for Autosome, autosomal and Pseudoautosomal region, pseudoautosomal genes. Here ''sets of chromosomes'' refers to the num ...

strains for experimental purposes.

References

{{Taxonbar, from=Q7396603 paradoxus Yeasts Fungi described in 1914 Yeasts used in brewing Fungus species