Killer toxin of Saccharomyces cerevisiae Y500-4L active against Fleischmann and Itaiquara commercial brands of yeast

the strain saccharomyces cerevisiae y500-4l, previously selected from the must of alcohol producing plants and showing high fermentative and killer capacities, was characterized according to the interactions between the yeasts and examined for curing and detection of dsrna plasmids, which code for the killer character. the killer yeast s. cerevisiae y500-4l showed considerable killer activity against the fleischmann and itaiquara commercial brands of yeast and also against the standard killer yeasts k2 (s. diastaticus ncyc 713), k4 (candida glabrata ncyc 388) and k11 (torulopsis glabrata atcc 15126). however s. cerevisiae y500-4l showed sensitivity to the killer toxin produced by the standard killer yeasts k8 (hansenula anomala ncyc 435), k9 (hansenula mrakii ncyc 500), k10 (kluyveromyces drosophilarum ncyc 575) and k11 (torulopsis glabrata atcc 15126). no m-dsrna plasmid was detected in the s. cerevisiae y500-4l strain and these results suggest that the genetic basis for toxin production is encoded by chromosomal dna. the strain s. cerevisiae y500-4l was more resistant to the loss of the phenotype killer with cycloheximide and incubation at elevated temperatures (40oc) than the standard killer yeast s. cerevisiae k1.