Assuntos
Metabolismo dos Lipídeos , Saccharomyces cerevisiae/crescimento & desenvolvimento , Cromatografia em Camada Fina , Meios de Cultura , Ácidos Graxos/análise , Ácidos Graxos/metabolismo , Lipídeos/análise , Lipídeos/isolamento & purificação , Microbiologia/instrumentação , Saccharomyces cerevisiae/análise , Saccharomyces cerevisiae/metabolismo , Solventes , Esporos Fúngicos/análise , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/metabolismo , Fatores de TempoRESUMO
There is currently a great interest by many winemakers in making some of their vinifications by means of pure culture yeasts. We describe, in this paper, the problems encountered in operating this way, the corresponding aims, the method of selecting strains and, more particularly, the possibilities offered by applying yeast genetics.
Assuntos
Saccharomyces/metabolismo , Vinho , Etanol/metabolismo , Fermentação , Tecnologia de AlimentosRESUMO
Electrophoretic karyotypes of two strains of Saccharomyces cerevisiae, a haploid laboratory strain and a wild strain known to be at least diploid, have been checked during vegetative growth. The karyotype of the haploid strain was very stable; however, the diploid strain underwent frequent modifications. In most cases the number of bands was reduced, but occasionally we observed one band splitting into two. In one case, chromosomal rearrangements took place between differently sized copies of chromosomes I and VI. We concluded that the chromosome length polymorphism observed among wild strains of S. cerevisiae could be explained partly by chromosomal structure reorganization occurring during mitosis.
Assuntos
Cromossomos Fúngicos/química , Rearranjo Gênico , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/genética , DNA Fúngico/análise , Haploidia , Polimorfismo Genético , Saccharomyces cerevisiae/fisiologia , Especificidade da Espécie , Esporos Fúngicos/fisiologiaRESUMO
Wine yeast strains are characterized by a high chromosomal DNA polymorphism. This can be explained partly by a size difference of different variants of specific chromosomes. This difference can reach up to 45% of the size of the chromosome in question. Two strains, SB1 and Eg8, have a very complex chromosomal pattern and show one band hybridizing with probes from two different chromosomes derived from a reference strain. This is an indication of the presence of "hybrid" chromosomes in these wine strains. The most astonishing result concerns chromosome VIII, frequently present in wine strains in two variant forms. The first normal form has a size of about 580 kb while the second is around 1000 kb. These two forms segregate at meiosis and recombine with a normal chromosome VIII from a laboratory strain. Wine yeasts are thus very different from haploid laboratory strains.
Assuntos
DNA Fúngico/genética , Polimorfismo Genético , Saccharomyces cerevisiae/genética , Southern Blotting , Cromossomos Fúngicos , Eletroforese em Gel de Campo Pulsado , Genes Fúngicos , Hibridização de Ácido Nucleico , VinhoRESUMO
A yeast flocculation gene was isolated from a genomic library of an FLO5 strain of S. cerevisiae on the basis of its ability to trigger flocculation in a non-flocculent strain. Characterization of the cloned gene by restriction mapping, Southern analysis, and chromosome mapping have shown that it corresponds to a FLO5 gene previously located on chromosome I and that this gene is related to the already described FLO1 gene. A study of gene expression in different yeast strains has indicated that, while this gene is dominant, its expression can be suppressed in some genetic backgrounds. A Northern-blot analysis has demonstrated that the same 5000-nt transcript was present in an FLO5 and an FLO1 strain. A gene disruption experiment has led to the conclusion that another flocculation gene is present and can be active in the FLO5 strain we used.
Assuntos
Regulação Fúngica da Expressão Gênica , Genes Fúngicos , Saccharomyces cerevisiae/genética , Mapeamento Cromossômico , Cromossomos Fúngicos , Clonagem Molecular , DNA Fúngico/genética , Fenótipo , Transcrição GênicaRESUMO
Evolution of cell wall during sporulation was studied by means of scanning electron microscopy and by immunological techniques. Experiments were done simultaneously with a strain a/alpha able to sporulate and a strain alpha/alpha unable to sporulate. Under such conditions it was possible to clarify whether the changes observed were related to the sporulation or to the culture conditions. Cell wall structure modifications during sporulation were not obvious morphologically but have been revealed by immunological methods. During vegetative growth, antigenic sites of strains a/alpha and alpha/alpha were different. During incubation in the sporulation medium, antigenic structure of the cell wall was modified. Some antigenic sites seem to be specific of sporulation.