Growth Inhibition of Free-Living Protozoa by Actidione

Abstract

13 strains of Tetrahymena geleii and Euglena gracilis var. bacillaris (colorless) were studied with respect to actidione tolerance. 1 [mu]./ml. or less, in a medium containing Bacto casitone and Bacto yeast extract at pH 5-6, markedly inhibited growth of all forms. Euglena, and T. geleii GP and Y did poorly with 5 [mu]g./ml. of the antibiotic. Of the remaining ciliates, strain S was the most highly resistant and was capable of growing at the 20 [mu]g. level. By employing a step-up transfer procedure, a variant of strain S was conditioned to a medium containing 50 [mu]g./ml. At pH levels above 6 actidione potency was lost.