Use of Toxins
The susceptibility to toxins varies greatly between yeast species and strains. Several experiments have made use of this to reliably identify strains. Morace, Archibusacci, Sestito and Polonelli (1984) used the toxins produced by 25 species of yeasts to differentiate between 112 pathogenic strains, based on their sensitivity to each toxin. This was extended by Morace et al. (1989) to use toxins to differentiate between 58 bacterial cultures. Vaughan-Martini, Cardinali and Martini (1996) used 24 strains of killer yeast from 13 species to find a resistance signature for each of 13 strains of S. cerevisiae used as starters in wine-making. Buzzini and Martini (2001) showed that sensitivity to toxins could be used to discriminate between 91 strains of Candida albicans and 223 other Candida strains.
Others experimented with using killer yeasts to control undesirable yeasts. Palpacelli, Ciani and Rosini (1991) found that Kluyveromyces phaffii was effective against Kloeckera apiculata, Saccharomycodes ludwigii and Zygosaccharomyces rouxii – all of which cause problems in the food industry. Polonelli et al. (1994) used a killer yeast to vaccinate against C. albicans in rats. Lowes et al. (2000) created a synthetic gene for the toxin HMK normally produced by Williopsis mrakii, which they inserted into Aspergillus niger and showed that the engineered strain could control aerobic spoilage in maize silage and yoghurt. Ciani and Fatichenti (2001) used a toxin-producing strain of Kluyveromyces phaffii to control apiculate yeasts in wine-making. Da Silvaa, Caladoa, Lucasa and Aguiar (2007) found a toxin produced by Candida nodaensis was effective at preventing spoilage of highly salted food by yeasts.
Several experiments suggest that antibodies that mimic the biological activity of killer toxins have application as antifungal agents.
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