View source for Saccharomyces paradoxus

{{Uncurated}}
{{Biorealm Genus}}

==Classification==

===Higher Order Taxa===

'''Domain:''' Eukaryota<br />
'''Kingdom:''' Fungi<br />
'''Subkingdom:''' Dikarya<br />
'''Phylum:''' Ascomycota<br />
'''Subphylum:''' Saccharomycotina<br />
'''Class:'''  Saccharomycetes<br />
'''Order:'''  Saccharomycetales<br />
'''Family:''' Saccharomycetaceae<br />
'''Genus:''' Saccharomyces<br />

===Species===

[http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=27291&lvl=3&lin=f&keep=1&srchmode=1&unlock Taxonomy of ''Saccharomyces paradoxus'']

==Description and significance==

''Saccharomyces paradoxus'' is a yeast species which can be found living on the bark of deciduous trees worldwide. It is the closest relative of ''Saccharomyces cerevisiae'', the most widely studied eukaryotic model organism. The two species diverged from a common ancestor species approximately 5 million years ago [[#References|[1]]]. Unlike its sister species, which has been used for brewing and baking for millenia, ''S. paradoxus'' has no domestic uses and consequently has been relatively unaffected by human interaction. Nevertheless, the two species are very similar, and ''S. paradoxus'' can easily be cultured in a laboratory setting in a manner similar to ''S. cerevisiae''. The non-domesticated ''S. paradoxus'' therefore is an attractive model organism for the study of the population genetics and genomics of wild yeast [[#References|[9]]].

==Genome structure==
In its haploid form, ''S. paradoxus'' has 16 linear chromosomes, with a total genome length of approximately 12 million base pairs. Analysis of the genome sequence found an anticipated 8,908 protein-encoding genes. The genome is highly conserved when compared to its sister species, ''S. cerevisiae''. In coding regions, its genome shares 90% of its identity with the genome of ''S. cerevisiae''; in intergenic regions, 80% [[#References|[1]]].

Artificially-created diploid F1 hybrids of ''S. cerevisiae'' and ''S. paradoxus'' are able to survive in culture; however, the haploid gamete daughter cells of the hybrid are not viable [[#References|[2]]].

==Cell structure, metabolism & life cycle==

''S. paradoxus'' is almost phenotypically indistinguishable from its closely-related counterpart, ''S. cerevisiae'', in nearly all aspects of morphology, metabolism, and life cycle. However, it is a phylogenetically distinct species, as haploid gametes of ''S. paradoxus'' and ''S. cerevisiae'' cannot combine into a viable diploid hybrid organism [[#References|[5]]].

===Cell Structure===

''S. paradoxus'' is a unicellular fungus with a chitinous cell wall. Externally, it appears spherical or ellipsoid in shape, with a diameter of 1-5 micrometers, dependent upon life cycle phase. Internally, it possesses a membrane-bound nucleus, a cytoskeleton, and mitochondria, as is typical for any eukaryotic organism [[#References|[7]]].

===Metabolism===

''S. paradoxus'' is a chemoorganotrophic organism, preferring glucose as a carbon source (though it possesses enzymes to convert certain other sugars into glucose.) It is capable of aerobic respiration via glycolysis and the TCA cycle, or ethanolic fermentation of glucose directly [[#References|[7]]].

===Life Cycle===

''S. paradoxus'' can exist in both haploid or diploid forms. In either state, asexual reproduction can occur through a mitotic process called budding, in which a daughter cell "bubbles out" from the mother cell. In the diploid state, sporulation can occur, a meiotic process in which a single diploid cell divides into four haploid spore. The spores themselves are capable of reproducing via budding in their haploid state, or fusing with other spores to form a diploid yeast cell [[#References|[7]]]. This is rare, however, as gamete fusion occurs only about once in every 1000 generatons; reproduction is primarily asexual [[#References|[9]]].

==Ecology (including pathogenesis)==
''S. paradoxus'' is found in exudates of oak tree bark, and in samples of oak-associated soil [[#References|[3]]]. It shares the same habitat with several other members of genus Saccharomyces (including ''S. cerevisiae'',) all of which possess nearly identical metabolic requirements. It is theorized that competitive exclusion does not occur because each species possesses specialized glycolytic enzymes with differing optimal temperature ranges [[#References|[4]]]. ''S. paradoxus'' grows optimally around 27-30 °C, markedly lower than the preferred temperature of 37 °C for ''S. cerevisiae'' [[#References|[5]]].

It is not a known pathogen, though ''S. cerevisiae'' is known to cause disease in humans in rare instances [[#References|[6]]].

==Interesting feature==

In a controlled study, the taste profile of Chardonnay wines fermented with wild strains of ''S. paradoxus'' compared favorably with a batch fermented with traditional brewer's yeast (''S. cerevisiae''), though ''S. cerevisiae'' was able to achieve a slightly higher terminal alcohol concentration [[#References|[8]]].

==References==
[1] [http://bio5495.wustl.edu/Project/439-Kellis-2003.pdf Kellis, M, et al. "Sequencing and comparison of yeast species to identify genes and regulatory elements." ''Nature''. 2003 May 15; 423(6937):241-54.]

[2] [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1797814/?tool=pubmed Grieg, D. "A Screen for Recessive Speciation Genes Expressed in the Gametes of F1 Hybrid Yeast." ''PLoS Genetics.'' 2007 February; 3(2): e21.]

[3] [http://www.ncbi.nlm.nih.gov/pubmed/10029999 Naumov, GI; Naumova, ES; Sniegowski, PD. "Saccharomyces paradoxus and Saccharomyces cerevisiae are associated with exudates of North American oaks." ''Canadian Journal of Microbiology.'' 1998 Nov; 44(11):1045-50.]

[4] [http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0020739 Gonçalves, P, et al. "Evidence for Divergent Evolution of Growth Temperature Preference in Sympatric Saccharomyces Species." ''PLoS ONE.'' 2011; 6(6): e20739.]

[5] [http://onlinelibrary.wiley.com/doi/10.1016/S1567-1356%2803%2900171-5/full#b3 Sweeney, JY; Kuehne, HA; Sniegowski, PD. "Sympatric natural Saccharomyces cerevisiae and S. paradoxus populations have different thermal growth profiles." ''FEMS Yeast Research.'' 2004 Jan; 4(4-5):521-5.]

[6] [http://cid.oxfordjournals.org/content/40/11/1625.long Muñoz, P, et al. "Saccharomyces cerevisiae fungemia: an emerging infectious disease." ''Clinical Infectious Diseases.'' 2005 Jun 1; 40(11):1625-34.]

[7] Dickinson, JR; Schweizer, M. ''The Metabolism and Molecular Physiology of Saccharomyces cerevisiae.'' 2004. London: Taylor &amp; Francis. Print.

[8] [http://bib.irb.hr/datoteka/287372.Orlic_ifs_1217.pdf Orlic, S, et al. "Influence of indigenous Saccharomyces paradoxus strains on Chardonnay wine fermentation aroma." ''International Journal of Food Science & Technology.'' 2007; 42(1):95-101.]

[9] [http://www.sciencedirect.com/science/article/pii/S1631069111001429 Liti, G; Schacherer, J. "The rise of yeast population genomics." ''Comptes Rendus Biologies.'' 2011 Aug-Sep; 334(8-9):612-9.]