Project description:Saccharomyces pastorianus lager brewing yeasts are domesticated hybrids of Saccharomyces cerevisiae and cold-tolerant Saccharomyces eubayanus. To better understand the contribution of both parental genomes to maltose metabolism in brewing wort, this study focuses on maltose transport in the S. eubayanus type strain CBS12357T/FM1318T. To obtain complete sequences of the MAL loci of this strain, a near-complete genome assembly was generated using the Oxford Nanopore Technology MinION sequencing platform. Except for CHRXII, all sixteen chromosomes were assembled as single contigs. Four loci harboring putative maltose transporter genes (SeMALT1-4), located in subtelomeric regions of CHRII, CHRV, CHRXIII and CHRXVI, were completely resolved. The near-identical loci on CHRV and CHRXVI strongly resembled canonical S. cerevisiae MAL loci, while those on CHRII and CHRXIII showed different structures suggestive of gene loss. Functionality of the SeMALT1-4-encoded transporters was confirmed by their ability to restore growth on maltose, but not on maltotriose, of a maltose-transport-deficient S. cerevisiae strain. Simultaneous CRISPR-Cas9-assisted deletion of SeMALT2 and SeMALT4, which shared 99.7 % sequence identity, eliminated growth of S. eubayanus CBS12357T on maltose. Transcriptome analysis of S. eubayanus CBS12357T established that, in maltose-grown cultures, SeMALT2 and SeMALT4 were expressed at much higher levels than SeMALT1 and SeMALT3, thus resolving the apparent discrepancy between heterologous expression and deletion studies. These results represent a first genomic and physiological characterization of maltose transport in S. eubayanus CBS12357T and provides a valuable resource for further industrial exploitation of this yeast.
Project description:Metabolomic profiles were compiled from oak and wine yeast parents, and their F2 hybrids. Included in this study are extraction controls.
Project description:Four hybrid yeast strains isolated from a variety of industrial substrates were hybridized to an array-CGH platform containing probes to query the whole genomes of seven different Saccharomyces species. For most of the strains we found evidence of multiple interspecific hybridization events and multiple introgressed regions. The strains queried were GSY205 (isolated from a cider fermentation), GSY505 (a contaminant from a lager beer fermentation), GSY2232 (a commercial wine yeast strain), and GSY312 (a commercial lager beer strain). Additionally, 3 different rare viable spores derived from laboratory-created interspecific S. cerevisiae-S. bayanus (aka S. uvarum) hybrids were queried, before and after evolution in chemostats, via S. cerevisiae-S. bayanus microarrays.