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Saccharomyces cerevisiae K7 (= NBRC 101557)

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close this sectionAbout this Microorganism

Photo by National Research Institute of Brewing

Sake is a traditional Japanese alcoholic beverage that is fermented from steamed rice by the concerted actions of filamentous fungi, such as Aspergillus oryzae, and yeast. Yeast cells produce ethanol, higher alcohols and their esters, organic acids and amino acids in sake brewing process. Hence, the choice of a yeast strain is one of the key brewing processes determining aroma and taste of sake products. Sake yeast strains are known to possess characteristics ideal for sake brewing, such as high ethanol productivity, good growth and fermentation at low temperature and aroma production.

Saccharomyces cerevisiae Kyokai No.7 (K7) (= NBRC 101557) was first isolated in 1946 from a sake brewery in Nagano Prefecture, Japan. K7 has been one of the most extensively used sake yeast strains during the past several decades. K7 also has been employed in numerous genetic and biochemical studies as a model sake yeast and as a parent strain for breeding. The 11.87 megabase (Mb) genome of K7 is composed of 16 chromosomes and mitochondrial DNA, and contains 6,209 genes. Although the entire assembled sequence and structure of the K7 genome were nearly identical to those of the standard laboratory strain S288C genome, subtelomeric polymorphisms and inverted regions were identified. Since K7 is a heterozygous diploid, a survey of heterozygous base positions identified 1,347 different nucleotides between two homologous chromosomes. These findings have provided the basis for future studies on genealogy and evolution of sake yeast, and may be clues for finding relationships among genotypes and phenotypes for good sake brewing.

close this sectionProject history

close this date 2014-01-07 ..... 1
2014-01-07 Important notice and apology -BLAST search against Saccharomyces cerevisiae K7 genome
imageAn error in BLAST search was discovered. Those who executed BLAST search against Saccharomyces cerevisiae K7 during the period from May 2012 to January 2014 could have gotten inappropriate search result. We have fixed an error and we deeply apologize to all DOGAN users.

close this sectionSummary of the genomic data

Genomic size (estimated)
11,881,178 bp
G+C content 38.37 %
Number of ORFs assigned 5,726
Percentage of the coding regions 66.45 %
Percentage of the intronic regions 0.71 %
Number of rRNA genes 7
Number of tRNA genes 296
Number of other features

close this sectionGeneral Procedure

The nucleotide sequence of the S. cerevisiae Kyokai No.7 genome was determined by whole genome shotgun sequencing methods as in the case of other organisms analyzed at NITE-DOB.

  • DNA shotgun libraries
    Plasmid libraries with average sizes of 1.6 and 5.0 kb were constructed in pUC118 (TaKaRa).

  • Fosmid library
    A Fosmid library with an average insert sizes of 35 kb was constructed in pCC1FOS (Epicentre).

  • Nucleotide Sequencing
    Raw sequence reads corresponding to 9.1-fold coverage of the haploid genome (42,842, 88,830 and 15,227 reads from libraries with 1.6-, 5.0- and 35-kb inserts, respectively) were obtained by sequencing on an ABI3730xl DNA Analyzer (ABI). Sequence reads were trimmed at a thresholds quality value of 20 by Phred and assembled by Phrap/Consed software.

  • Validation of the assembled sequence data
    The overall assembly was then validated and refined using Optical Mapping (OpGen Inc.). A number of short contigs were incorporated into supercontigs with the assistance of the optical maps and the transposon-mediated random sequencing of fosmid clones.

  • Gene identification and annotation
    ORF prediction was conducted based on direct comparison of S288C ORFs with the K7 genome ORFs larger than 90-bp were comprehensively included as candidates. When direct comparison was difficult, ORFs were predicted using the programs CRITICA, Glimmer2, GlimmerHMM and SIM4. All ORFs were manually validated and annotated. Functional annotation was based primarily on the Saccharomyces Genome Database (SGD), and secondarily, on another Saccharomyces species database, COG, UniProtKB and non-redundant databases.

close this sectionRelated links to external databases