Action of yeast killer factor: a resistant mutant with sensitive spheroplasts.

Journal of Bacteriology (Impact Factor: 3.19). 04/1973; 113(3):1193-7.
Source: PubMed

ABSTRACT Yeast killer factor proteins bind to cells of both sensitive and killer-producing strains, although the latter are immune to killer action. Spheroplasts prepared from sensitive cells bind less than 1% of the killer bound to whole cells, but remain fully sensitive to killer. This finding and those obtained from binding studies of partially purified, radioactive killer protein suggest that most of the toxins remain bound to the yeast cell wall and do not function further in the killing process. A killer-resistant mutant R(18) was isolated from a sensitive strain. Whole cells of the mutant were unable to bind killer and were fully resistant. In contrast, spheroplasts of R(18) were fully sensitive to killer. These data suggest that the sites exposed to killer in spheroplasts are distinct from those on the cell wall. These wall sites appear to be necessary for killer action in whole cells.

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    ABSTRACT: Killer yeasts are frequently used to combat and prevent contamination by wild-type yeasts during wine production and they can even dominate the wine fermentation. Stuck and sluggish fermentations can be caused by an unbalanced ratio of killer to sensitive yeasts in the bioreactor, and therefore it is important to determine the proportion of both populations. The aim of this study was to provide a simple tool to monitor killer yeast populations during controlled mixed microvinifications of killer and sensitive Saccharomyces cerevisiae. Samples were periodically extracted during vinification, seeded on Petri dishes and incubated at 25 and 37 °C; the latter temperature was assayed for possible inactivation of killer toxin production. Colonies developed under the described conditions were randomly transferred to killer phenotype detection medium. Significant differences in the killer/sensitive ratio were observed between both incubation temperatures in all microvinifications. These results suggest that 37 °C seems a better option to determine the biomass of sensitive yeasts, in order to avoid underestimation of sensitive cells in the presence of killer yeasts during fermentations. Incubation at a toxin-inhibiting temperature clearly showed the real ratio of killer to sensitive cells in fermentation systems.
    World Journal of Microbiology and Biotechnology (Formerly MIRCEN Journal of Applied Microbiology and Biotechnology) 07/2012; 28(11):3135-42. · 1.35 Impact Factor
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    ABSTRACT: The aim of this work was to study the production of functional protein in yeast culture. The cells of Saccharomyces cerevisiae Embrapa 1B (K+R+) killed a strain of Saccharomyces cerevisiae Embrapa 26B (K-R-)in grape must and YEPD media. The lethal effect of toxin-containing supernatant and the effect of aeration upon functional killer production and the correlation between the products of anaerobic metabolism and the functional toxin formation were evaluated. The results showed that at low sugar concentration, the toxin of the killer strain of Sacch. cerevisiae was only produced under anaerobic conditions . The system of killer protein production showed to be regulated by Pasteur and Crabtree effects. As soon as the ethanol was formed, the functional killer toxin was produced. The synthesis of the active killer toxin seemed to be somewhat associated with the switch to fermentation process and with concomitant alcohol dehydrogenase (ADH) activity.
    Brazilian Archives of Biology and Technology 01/2011; 54(3):601-612. · 0.47 Impact Factor
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    ABSTRACT: Treatment of sensitive cells of Saccharomyces cerevisiae with killer toxin KT28 affected cell viability after 2 h; the effect was dependent upon the availability of a utilizable energy source. Treatment led to an interruption of cell growth. The mother cells contained nuclear DNA, whereas their daughter buds did not. Using a killer-toxin-sensitive thymidine auxotroph of S. cerevisiae carrying a temperature-sensitive thymidylate uptake mutation, it was shown that the incorporation of dTMP at the permissive temperature was inhibited within 30min of the addition of KT28. When cells labelled at the permissive temperature were incubated at the restrictive temperature, the level of radioactivity declined in the absence but not in the presence of KT28. No other effects of KT28 were observed within 2 h of its addition, and it is concluded that the inhibition of DNA synthesis is an early effect of the action of KT28.
    Microbiology-sgm. 01/1989; 135(6):1529-1535.


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