E. J. Middelbeek

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Production of the killer toxin of Pichia kluyveri 1002 was stimulated in the presence of yeast extract. In a minimal medium production was optimal at pH 3.8–4.0 and 22–25°C. Addition of gelatin and nonionic detergents, like Brij-58 (polyoxyethylene 20 cetyl ether) and Triton-X-100, to this medium enhanced production significantly. The killer toxin was(More)
Among yeast strains of human origin belonging to the genera Candida, Cryptococcus, Torulopsis, and Rhodotorula which were examined for killer and sensitive characteristics with killer and sensitive strains of Cryptococcus, Hansenula, Kluyveromyces, Pichia, Saccharomyces, and Torulopsis as screening organisms, a high incidence of sensitivity to killer toxins(More)
Yeast strains (157) belonging to at least 9 genera were isolated from natural habitats and screened for killer-sensitive relationships. Killer and sensitive characteristics were exhibited by 17 and 11 percent of the isolates, respectively. The strains belong to either one of two mutually exclusive killer-sensitive groups.
The killer toxin produced by Pichia kluyveri 1002 kills yeast strains of the genera Candida, Saccharomyces and Torulopsis, including several S. cerevisiae killer strains. Binding of a lethal amount of the toxin to cells of S. cerevisiae SCF 1717 occurs rapidly after toxin addition. After treatment with the toxin for 10 min sensitive cells partially(More)
Loss of viability of toxin-treated cells of Saccharomyces cerevisiae SCF 1717 could be prevented in the period before they altered physiologically if cells were incubated in media with a suitable concentration of potassium (0.08 to 0.13 M) and hydrogen ions (pH 6.2 to 6.7). Incorporation of higher amounts of potassium chloride in the media had a pronounced(More)
The interaction between the killer toxin of Pichia kluyveri 1002 and cells of Saccharomyces cerevisiae SCF 1717 is strongly affected by the physiological state of sensitive cells. The killing effect is maximal for cells in the lag and early exponential phase of growth, whereas stationary cells are completely resistant. Furthermore, sensitivity is markedly(More)
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