Vol. 12, Issue 6 (2023)

Author(s):
Uma Sankareswari R, Punitha A, Subha L, Geethalakshmi I, Sumathi T and Adeline Vinila JE

Abstract:
The first reports regarding their killer phenotype date to over 50 years ago, with the initial isolation of a Saccharomyces cerevisiae strain that inhibited the growth of other S. cerevisiae strains. Currently, the killer yeasts belonging to this species have been classified into three main groups (K1, K2, and K28) on the basis of the molecular characteristics of the secreted toxins, their killing profiles, the lack of cross-immunity, and the encoding genetic determinants. Killer strains of Ustilago maydis can secrete one of the three different toxins that have been identified so far. Many types of killer toxins have been reported and their genomes were mapped on double-stranded RNA (S. cerevisiae K1, K2, K28, Ustilage maydis and Hanseniaspora uvarum), a linear double-stranded DNA plasmid (Kluyveromyces lactis, Pichia acaciae and Pichia inositovora) or carried on a chromosome (S. cerevisiae KHS, KHR and Williopsismrakii). During the last two decades, secreted killer toxins and toxin-producing killer yeasts have found several applications. For instance in the food and fermentation industries, Killer yeasts have been used to combat contaminating wild-type yeasts which can occur during the production of wine, beer and bread. Killer yeasts have also been used as bio-control agents in the preservation of foods, in the bio-typing of medically important pathogenic yeasts and yeast-like fungi.