Saccharomyces pastorianus

Taxobox
name = "Saccharomyces pastorianus"
regnum = Fungi
phylum = Ascomycota
subphylum = Saccharomycotina
classis = Saccharomycetes
ordo = Saccharomycetales
familia = Saccharomycetaceae
genus = "Saccharomyces"
species = "S. pastorianus"
binomial = "Saccharomyces pastorianus"
binomial_authority = Nguyen & Gaillardin ex. Beijerinck
synonyms = "Saccharomyces carlsbergensis"

"Saccharomyces pastorianus" is a yeast, used industrially for the production of lager beer. It is a synonym of the yeast species "Saccharomyces carlsbergensis"Casaregola S, et al. (2001), [http://ijs.sgmjournals.org/cgi/reprint/51/4/1607 "Analysis of the constitution of the beer yeast genome by PCR, sequencing and subtelomeric sequence hybridization."] , Int J Syst Evol Microbiol 51(Pt 4):1607-18.] , which was originally described in 1883 by Emil Christian Hansen, who was working for the Danish brewery Carlsberg.

Genomics

As "S. pastorianus" is a hybrid of "Saccharomyces bayanus" and "Saccharomyces cerevisiae" it is not surprising that there is a degree of phenotypic and genomic similarity between the two species. [Tamai Y, Momma T, Yoshimoto H, Kaneko Y., [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?holding=npg&cmd=Retrieve&db=PubMed&list_uids=9717238&dopt=Abstract Co-existence of two types of chromosome in the bottom fermenting yeast, Saccharomyces pastorianus.] , Yeast. 1998 Jul;14(10):923-33.] The hybrid nature of "S. pastorianus" also explains the genome size, which is up to 60% larger than that of "S. cerevisiae" as it includes large parts of the two genomesMontrocher R "et al" (1998), [http://ijs.sgmjournals.org/cgi/reprint/48/1/295.pdf Phylogenetic Analysis of the Saccharomyces cerevisiae Group Based on Polymorphisms of the rDNA Spacer Sequences] , Int. J. Syst. Bacteriol., vol 48, pp 295–303] . However there is growing evidence that "S. pastorianus" has inherited most of its genetic material from "S. bayanus". Indeed the mitochondrial DNAPiskur, J., S. Smole, C. Groth, R.F. Petersen and M.B. Pedersen (1998), [http://ijs.sgmjournals.org/cgi/content/abstract/48/3/1015 Structure and genetic stability of mitochondrial genomes vary among yeasts of the genus Saccharomyces.] Int. J. System. Bacteriol. 48: 1015-1024.] and ribosomal DNA of "S. pastorianus" appear to be derived from "S. bayanus" rather than "S. cerevisiae".

The genomic difference between "S. pastorianus" and "S. cerevisiae" is responsible for a number of phenotypic traits which "S. pastorianus" share with "S. bayanus", but not "S. cerevisiae". The ability of "S. pastorianus" to break down melibiose is dependent on up to ten MEL genes, which are exclusive to strains metabolising melibose such as "S. bayanus". "S. pastorianus" never grows above 34°C, whereas "S. cerevisiae" will grow at 37°C. "S. pastorianus" exhibits a higher growth rate than "S. cerevisiae" at 6 to 12°C.

It has been suggested that "S. pastorianus" may be a hybrid of "S. cerevisiae" and "Saccharomyces monacensis", as the LEU2, MET2 and ACB1 genes of "S. pastorianus" had been reported to have a high level of similarity or be identical to the "S. monacensis" homologues Hansen J and Kielland-Brandt MC (1994), [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T39-47PNX4N-B3&_coverDate=12%2F31%2F1994&_alid=512875340&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4941&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=ee8b387b7dd2fe32888a8cc8272d31d6 Saccharomyces carlsbergensis contains two functional MET2 alleles similar to homologues from S. cerevisiae and S. monacensis.] Gene 140(1):33-40] [Casey GP, Pedersen MB (1988), [http://db.yeastgenome.org/cgi-bin/reference/reference.pl?dbid=S000078250 DNA sequence polymorphisms in the genus Saccharomyces. V. Cloning and characterization of a LEU2 gene from S. carlsbergensis.] Carlsberg Res Commun 53(3):209-19] [Borsting C, et al. (1997), [http://db.yeastgenome.org/cgi-bin/reference/reference.pl?dbid=S000040754 Saccharomyces carlsbergensis contains two functional genes encoding the acyl-CoA binding protein, one similar to the ACB1 gene from S. cerevisiae and one identical to the ACB1 gene from S. monacensis.] Yeast 13(15):1409-21] . However, subtelomeric sequence hybridisation has suggested that "S. monacensis" is likely to be a closely related hybrid to "S. pastorianus", rather than an ancestor.

Ale strains are genetically more diverse than lager strains, as lager strains are thought to derive from a hybrid gene pool (Casey, 1996). It is thought that the lager strains in use are derived from only one or two primary strains; Tuborg and Carlsberg (Casey, 1990; Casey, 1996).

"Saccharomyces uvarum"

"Saccharomyces uvarum" is a species of yeast that is believed to have originated as a hybrid of "S. cerevisiae" and "S. monacensis", because of its allopolyploid genomeFact|date=February 2007. It is a bottom-fermenting yeast, so-called because it does not form the foam on top of the wort that "top-fermenting yeast" does.

Further research was done by Martinus Willem Beijerinck in 1898, it was synonymized with "S. bayanus" but revived by Nguyen & Gaillardin in 2005. [H. V. Nguyen & C. Gaillardin, [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6W8C-4F53M0J-3&_coverDate=02%2F01%2F2005&_alid=303234053&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6651&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=496cde5928b0b7e6631a1c102ff95a26 Evolutionary relationships between the former species "Saccharomyces uvarum" and the hybrids "Saccharomyces bayanus" and "Saccharomyces pastorianus"; reinstatement of "Saccharomyces uvarum" (Beijerinck) as a distinct species.] , FEMS Yeast Research (2005) vol 5, pp 471–483] [ [http://www.epa.gov/oppt/biotech/pubs/fra/fra010.htm "Saccharomyces uvarum" at EPA.gov] ]

ee also

*Brewing
*Bottom and top fermenting yeast
*Lager
*Yeast

References