The occurrence of killer characters in yeasts.

Strains of the genera Saccharomyces, Saccharomycodes, Schizosaccharomyces, Hanseniaspora, Kluyveromyces, Pichia, Kloeckera, and Torulopsis were examined for killer, sensitive, neutral, and killer-sensitive characteristics against a killer strain (NCYC738) and a sensitive strain (NYCC1006) of Saccharomyces cerevisiae. Thirty-one Saccharomyces cerevisiae strains out of 782 screened were able to kill the sensitive test strain; 707 appeared to be sensitive and 44 neutral. A high frequency of killer phenotypes (71.4%) was found in Hansenula anomala var. anomala strains. No killer strains were present in the remaining 17 species considered.