Curing of a Killer Factor in Saccharomyces cerevisiae

Many standard laboratory stocks of yeast are able to kill other yeast strains. This property has not been generally recognized because killing is observed only at low pH and not at the pH of standard media. In all strains examined, the genetic determinant for the killer trait shows non-Mendelian inheritance. The segregation patterns of our killer strains indicate that this killer determinant may be different from the killer previously described. Treatment of a killer strain with cycloheximide, but not with ethidium bromide, converts it into a sensitive nonkiller.