Killer toxins of certain yeast strains have potential growth inhibitory activity on gram-positive pathogenic bacteria

The killer yeast strains which are encountered most frequently among species in the genera Saccharomyces, Candida, Hansenula, Pichia and Kluyveromyces (ten killer strains in toto) were tested for the activity of their toxins on the growth of some pathogenic bacteria (four Gram-positive and six Gram-negative strains) in a test in which purified toxins were not required. Neither toxins of the killer Saccharomyces cerevisiae and Pichia membranefaciens strains were active against the bacterial strains. In contrast the killer toxins of Hansenula anamola, Hansenula mrakii, Candida tropicalis, Kluyveromyces drosphilarum and Kluyveromyces lactis showed potential growth inhibitory effects on Gram-positive pathogenic bacteria. Thus, yeast killer toxins were found to be active only on Gram-positive bacterial cell types.