Project description:This work describes, for the first time, the genome sequence of a Saccharomycodes ludwigii strain. Although usually seen as a wine spoilage yeast, S. ludwigii has been of interest for the production of fermented beverages because it harbors several interesting properties, including the production of beneficial aroma compounds.
Project description:BackgroundIntermixing of genomes through meiotic reassortment and recombination of homologous chromosomes is a unifying theme of sexual reproduction in eukaryotic organisms and is considered crucial for their adaptive evolution. Previous studies of the budding yeast species Saccharomycodes ludwigii suggested that meiotic crossing over might be absent from its sexual life cycle, which is predominated by fertilization within the meiotic tetrad.ResultsWe demonstrate that recombination is extremely suppressed during meiosis in Sd. ludwigii. DNA double-strand break formation by the conserved transesterase Spo11, processing and repair involving interhomolog interactions are required for normal meiosis but do not lead to crossing over. Although the species has retained an intact meiotic gene repertoire, genetic and population analyses suggest the exceptionally rare occurrence of meiotic crossovers in its genome. A strong AT bias of spontaneous mutations and the absence of recombination are likely responsible for its unusually low genomic GC level.ConclusionsSd. ludwigii has followed a unique evolutionary trajectory that possibly derives fitness benefits from the combination of frequent mating between products of the same meiotic event with the extreme suppression of meiotic recombination. This life style ensures preservation of heterozygosity throughout its genome and may enable the species to adapt to its environment and survive with only minimal levels of rare meiotic recombination. We propose Sd. ludwigii as an excellent natural forum for the study of genome evolution and recombination rates.
Project description:Non-Saccharomyces yeasts have received increased attention by researchers and winemakers, due to their particular contributions to the characteristics of wine. In this group, Saccharomycodes ludwigii is one of the less studied species. In the present study, a native S. ludwigii strain, UTAD17 isolated from the Douro wine region was characterized for relevant oenological traits. The genome of UTAD17 was recently sequenced. Its potential use in winemaking was further evaluated by conducting grape-juice fermentations, either in single or in mixed-cultures, with Saccharomyces cerevisiae, following two inoculation strategies (simultaneous and sequential). In a pure culture, S. ludwigii UTAD17 was able to ferment all sugars in a reasonable time without impairing the wine quality, producing low levels of acetic acid and ethyl acetate. The overall effects of S. ludwigii UTAD17 in a mixed-culture fermentation were highly dependent on the inoculation strategy which dictated the dominance of each yeast strain. Wines whose fermentation was governed by S. ludwigii UTAD17 presented low levels of secondary aroma compounds and were chemically distinct from those fermented by S. cerevisiae. Based on these results, a future use of this non-Saccharomyces yeast either in monoculture fermentations or as a co-starter culture with S. cerevisiae for the production of wines with greater expression of the grape varietal character and with flavor diversity could be foreseen.
Project description:BackgroundSaccharomycodes ludwigii belongs to the poorly characterized Saccharomycodeacea family and is known by its ability to spoil wines, a trait mostly attributable to its high tolerance to sulfur dioxide (SO2). To improve knowledge about Saccharomycodeacea our group determined whole-genome sequences of Hanseniaspora guilliermondii (UTAD222) and S. ludwigii (UTAD17), two members of this family. While in the case of H. guilliermondii the genomic information elucidated crucial aspects concerning the physiology of this species in the context of wine fermentation, the draft sequence obtained for S. ludwigii was distributed by more than 1000 contigs complicating extraction of biologically relevant information. In this work we describe the results obtained upon resequencing of S. ludwigii UTAD17 genome using PacBio as well as the insights gathered from the exploration of the annotation performed over the assembled genome.ResultsResequencing of S. ludwigii UTAD17 genome with PacBio resulted in 20 contigs totaling 13 Mb of assembled DNA and corresponding to 95% of the DNA harbored by this strain. Annotation of the assembled UTAD17 genome predicts 4644 protein-encoding genes. Comparative analysis of the predicted S. ludwigii ORFeome with those encoded by other Saccharomycodeacea led to the identification of 213 proteins only found in this species. Among these were six enzymes required for catabolism of N-acetylglucosamine, four cell wall β-mannosyltransferases, several flocculins and three acetoin reductases. Different from its sister Hanseniaspora species, neoglucogenesis, glyoxylate cycle and thiamine biosynthetic pathways are functional in S. ludwigii. Four efflux pumps similar to the Ssu1 sulfite exporter, as well as robust orthologues for 65% of the S. cerevisiae SO2-tolerance genes, were identified in S. ludwigii genome.ConclusionsThis work provides the first genome-wide picture of a S. ludwigii strain representing a step forward for a better understanding of the physiology and genetics of this species and of the Saccharomycodeacea family. The release of this genomic sequence and of the information extracted from it can contribute to guide the design of better wine preservation strategies to counteract spoilage prompted by S. ludwigii. It will also accelerate the exploration of this species as a cell factory, specially in production of fermented beverages where the use of Non-Saccharomyces species (including spoilage species) is booming.
Project description:During fermentation Saccharomyces yeast produces various aroma-active metabolites determining the different characteristics of aroma and taste in fermented beverages. Amino acid utilization by yeast during brewer´s wort fermentation is seen as linked to flavour profile. To better understand the relationship between the biosynthesis of aroma relevant metabolites and the importance of amino acids, DNA microarrays were performed for Saccharomyces cerevisiae strain S81 and Saccharomyces pastorianus var. carlsbergensis strain S23, respectively. Thereby, changes in transcription of genes were measured, which are associated with amino acid assimilation and its derived aroma-active compounds during fermentation.