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  • 1
    ISSN: 1432-0983
    Keywords: Key wordsSaccharomyces cerevisiae ; Enological yeast ; Transcription ; Alcoholic fermentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The adaptation of yeasts to industrial environments is thought to be largely dependent on gene-expression specificity. To assess the transcriptional specificity of an enological strain, we performed a pilot experiment and examined the transcript level of 99 ORFs of the chromosome-III right arm with two strains, an enological-derived strain and a laboratory strain, grown under three different physiological conditions: respiration, standard alcoholic fermentation and enological alcoholic fermentation. The use of 99 single ORF-derived probes led to the detection of 49 transcripts, most of which were present at low levels and were not regulated. Ethanol respiration induced transcripts, in a similar manner with both strains. While standard alcoholic fermentation led to only minor regulations, the enological fermentation conditions triggered the expression of different genes. In addition, a specific transcriptional response to these conditions was observed with the enological-derived strain. The known or predicted functions of several genes induced under enological conditions is related to either alcoholic fermentation or stress, suggesting that their specific induction could reflect adaptation of the strain to the enological environment. Our data suggest that systematic transcriptional studies are an effective way to assess the molecular basis of yeast adaptation to industrial environments.
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  • 2
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Saccharomyces cerevisiae PAU genes constitute the largest multigene family in yeast, with 23 members located mainly in subtelomeric regions. The role and regulation of these genes were previously unknown. We detected PAU gene expression during alcoholic fermentation. An analysis of PAU gene regulation using PAU–lacZ fusions and Northern analyses revealed that they were regulated by anaerobiosis. PAU genes display, however, different abilities to be induced by anaerobiosis and this appears to be related to their chromosomal localization; two subtelomeric copies are more weakly inducible than an interstitial one. We show that PAU genes are negatively regulated by oxygen and repressed by haem. Examination of PAU gene expression in rox1Δ and tup1Δ strains indicates that PAU repression by oxygen is mediated by an unknown, haem-dependent pathway, which does not involve the Rox1p anaerobic repressor but requires Tup1p. Given the size of the gene family, PAU genes could be expected to be important during yeast life and some of them probably help the yeast to cope with anaerobiosis.
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  • 3
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The world’s soils store more carbon than is present in biomass and in the atmosphere. Little is known, however, about the factors controlling the stability of soil organic carbon stocks and the response of the soil carbon pool to climate change remains uncertain. We investigated the ...
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  • 4
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; flocculation ; FLO1 ; surface protein ; repeated sequences ; expression ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The sequencing of a 6619 bp region encoding for a flocculation gene previously cloned from a strain defined as FLO5 (Bidard et al., 1994) has revealed that it was a FLO1 gene. The FLO1 gene product has been localized at the cell surface of the yeast cell by immunofluorescent microscopy. The Flo1 protein contains four regions with repeated sequences which account for about 70% of the amino acids of this protein. A functional analysis of the major repeated region has revealed that it plays an important role in determining the flocculation level. A gene disruption experiment has shown that the FLO5 strain STX 347-1D contains at least two flocculation genes of the FLO1 type but that they are supposed to be inactive and do not contribute to its flocculation. However, enzyme-linked immunosorbent assays performed on intact cells have revealed that a protein expressed at the cell surface of the FLO5 strain STX 347-1D is antigenically related to Flo1p. A deletion analysis of the 5′ region of the FLO1 gene has shown that the expression is submitted to controls which depend on the genetic background of the strain.
    Additional Material: 9 Ill.
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  • 5
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; alcoholic fermentation ; glycerol ; glycerol 3-phosphate dehydrogenase ; redox balance ; metabolic engineering ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The possibility of the diversion of carbon flux from ethanol towards glycerol in Saccharomyces cerevisiae during alcoholic fermentation was investigated. Variations in the glycerol 3-phosphate dehydrogenase (GPDH) level and similar trends for alcohol dehydrogenase (ADH), pyruvate decarboxylase and glycerol-3-phosphatase were found when low and high glycerol-forming wine yeast strains were compared. GPDH is thus a limiting enzyme for glycerol production. Wine yeast strains with modulated GPD1 (encoding one of the two GPDH isoenzymes) expression were constructed and characterized during fermentation on glucose-rich medium. Engineered strains fermented glucose with a strongly modified [glycerol] : [ethanol] ratio. gpd1Δ mutants exhibited a 50% decrease in glycerol production and increased ethanol yield. Overexpression of GPD1 on synthetic must (200 g/l glucose) resulted in a substantial increase in glycerol production (×4) at the expense of ethanol. Acetaldehyde accumulated through the competitive regeneration of NADH via GPDH. Accumulation of by-products such as pyruvate, acetate, acetoin, 2,3 butane-diol and succinate was observed, with a marked increase in acetoin production. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 5 Ill.
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  • 6
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; plasma membrane purification ; vesicles reconstitution ; K+/H+-exchange ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The existence of a K+/H+ transport system in plasma membrane vesicles from Saccharomyces cerevisiae is demonstrated using fluorimetric monitoring of proton fluxes across vesicles (ACMA fluorescence quenching). Plasma membrane vesicles used for this study were obtained by a purification/reconstitution protocol based on differential and discontinuous sucrose gradient centrifugations followed by an octylglucoside dilution/gel filtration procedure. This method produces a high percentage of tightly-sealed inside-out plasma membrane vesicles. In these vesicles, the K+/H+ transport system, which is able to catalyse both K+ influx and efflux, is mainly driven by the K+ transmembrane gradient and can function even if the plasma membrane H+-ATPase is not active. Using the anionic oxonol VI and the cationic DISC2(5) probes, it was shown that a membrane potential is not created during K+ fluxes. Such a dye response argues for the presence of a K+/H+ exchange system in S. cerevisiae plasma membrane and established the non-electrogenic character of the transport. The maximal rate of exchange is obtained at pH 6·8. This reversible transport system presents a high selectivity for K+ among other monovalent cations and a higher affinity for the K+ influx into the vesicles (exit from cells). The possible role of this K+/H+ exchange system in regulation of internal potassium concentration in S. cerevisiae is discussed.
    Additional Material: 11 Ill.
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  • 7
    ISSN: 0749-503X
    Keywords: wine yeasts ; alcoholic fermentation ; stationary phase ; nitrogen limitation ; Northern analysis ; heat-shock promoter ; HSP30::lacZ fusion ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Genetic engineering of wine yeast strains requires the identification of gene promoters specifically activated under wine processing conditions. In this study, transcriptional activation of specific genes was followed during the time course of wine fermentation by quantifying mRNA levels in a haploid wine strain of Saccharomyces cerevisiae grown on synthetic or natural winery musts. Northern analyses were performed using radioactive probes from 19 genes previously described as being expressed under laboratory growth conditions or on molasses in S. cerevisiae during the stationary phase and/or under nitrogen starvation. Nine genes, including members of the HSP family, showed a transition-phase induction profile. For three of them, mRNA transcripts could be detected until the end of the fermentation. Expression of one of these genes, HSP30, was further studied using a HSP30::lacZ fusion on both multicopy and monocopy expression vectors. The production of β-galactosidase by recombinant cells was measured during cell growth and fermentation on synthetic and natural winery musts. We showed that the HSP30 promoter can induce high gene expression during late stationary phase and remains active until the end of the wine fermentation process. Similar expression profiles were obtained on five natural winery musts. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; Schizosaccharomyces pombe ; Lactococcus lactis ; malolactic enzyme ; malolactic fermentation ; heterologous expression ; NMR ; Life Sciences ; Life Sciences (general)
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The ability of yeast strains to perform both alcoholic and malolactic fermentation in winemaking was studied with a view to achieving a better control of malolactic fermentation in enology. The malolactic gene of Lactococcus lactis (mleS) was expressed in Saccharomyces cerevisiae and Schizosaccharomyces pombe. The heterologous protein is expressed at a high level in cell extracts of a S. cerevisiae strain expressing the gene mleS under the control of the alcohol dehydrogenase (ADH1) promoter on a multicopy plasmid. Malolactic enzyme specific activity is three times higher than in L. lactis extracts. Saccharomyces cerevisiae expressing the malolactic enzyme produces significant amounts of l-lactate during fermentation on glucose-rich medium in the presence of malic acid. Isotopic filiation was used to demonstrate that 75% of the l-lactate produced originates from endogenous l-malate and 25% from exogenous l-malate. Moreover, although a small amount of exogenous l-malate was degraded by S. cerevisiae transformed or not by mleS, all the exogenous degraded l-malate was converted into l-lactate via a malolactic reaction in the recombinant strain, providing evidence for very efficient competition of malolactic enzyme with the endogenous malic acid pathways. These results indicate that the sole limiting step for S. cerevisiae in achieving malolactic fermentation is in malate transport. This was confirmed using a different model, S. pombe, which efficiently degrades l-malate. Total malolactic fermentation was obtained in this strain, with most of the l-malate converted into l-lactate and CO2. Moreover, l-malate was used preferentially by the malolactic enzyme in this strain also.
    Additional Material: 6 Ill.
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  • 9
    ISSN: 0749-503X
    Keywords: flocculation ; immunolocalization ; mannoprotein ; cell wall ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The yeast FLO genes encode cell surface proteins which are expected to play a major role in the control of flocculation. We have assessed the availability of the Flo proteins at the cell surface during the growth of two flocculent strains, ABXL-1D (FLO1) and STX347-1D (FLO5) using immunological approaches, enzyme-linked immunosorbent assays and immunofluorescence. Our data show that they are not permanently present at the cell surface but that their amount increases during growth. With both strains the flocculation level is tightly correlated to the amount of Flop antigen detected, suggesting that it is the availability of the Flo proteins at the cell surface which determines the flocculation level. Our data are consistent with the idea that the Flo proteins correspond to the flocculation lectins. The differences of flocculation pattern among strains could originate from variations in the regulation of the expression of the FLO genes. Monitoring of the distribution of the Flo proteins during cellular development revealed that they are incorporated essentially in the cell wall of growing buds. Incorporation of the Flo proteins in the cell wall displays a highly polarized aspect, at the bud tip and at the mother-daughter neck junction, which can persist in mature cells. Such a localization could be relevant to constraints of the cell wall incorporation of the mannoproteins. Depending on the regulation of Flop expression and on the incorporation of the proteins in the cell wall, a yeast population can be highly heterogeneous in Flo protein equipment. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 1546-1696
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: [Auszug] We describe the construction of a Saccharomyces cerevisiae strain expressing the gene encoding the L(+)–lactate dehydrogenase [L(+)–LDH)] from Lactobacillus casei. The recombinant strain is able to perform a mixed lactic acid–alcoholic fermenation. Yeast cells expressing the ...
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