title: Reversal by calcium ions of the growth inhibition of Debaryomyces nicotianae caused by antifungal polyene antibiotics.
abstract: Only Debaryomyces nicotianae strain 77, of seven different yeast strains tested, was found to be resistant to heptamycin and other antifungal heptaenes when grown in a rich medium. This strain, however, like the other six, was completely susceptible to these antibiotics in a minimal medium. Addition of yeast extract to the minimal medium abolished the heptamycin effect; calcium ions fully duplicated the effect of yeast extract; Mg(2+) and Mn(2+) were also effective but less so than Ca(2+). Ca(2+) also counteracted the activity of the heptaenes ascosin and trichomycin. Complete reversal of the polyene inhibition by Ca(2+) was obtained if the cation was added simultaneously with the antibiotic; addition of Ca(2+) 2 hr after the polyene was without effect. Addition of Ca(2+) in the absence of the polyene caused a slight, if any, growth stimulation of D. nicotianae 77. Cholesterol also counteracted polyene activity; this was due to the formation of a complex with the antibiotic which prevented the polyene from reaching the site of action-the cytoplasmic membrane. No evidence for complex formation between heptamycin and calcium was found. The importance of Ca(2+) in membrane structure, as evidenced from heptaene studies, is discussed.
mesh_terms: D000935:Antifungal Agents / Q000037:antagonists & inhibitors*; D001203:Ascomycota / Q000187:drug effects*; D002118:Calcium / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects; D011090:Polyenes / Q000037:antagonists & inhibitors*; D012440:Saccharomyces / Q000187:drug effects
chemical_list: D000935:Antifungal Agents; D011090:Polyenes; D002118:Calcium