The Effects of Selected Antibiotics on Pure Cultures of Algae

H unter , E. O., J r ., and I lda M c V eigh . (Vanderbilt U., Nashville, Tenn.) The effects of selected antibiotics on pure cultures of algae. Amer. Jour. Bot. 48(2): 179–185. 1961.—A determination was made of the effectiveness of various concentrations of actidione, nystatin, amphotericin‐A, anisomycin, and sulfocidin, antibiotics active primarily against fungi, in inhibiting representative species of Myxophyceae, Chlorophyceae, Bacillariophyceae, Xanthophyceae, and Euglenophyceae. Similar investigations were made using polymyxin‐B sulfate and bacitracin, antibiotics inhibitory to certain groups of bacteria. Concentrations of 1, 2, 20, 50, 100, and 200 p.p.m. were used. Concentrations of 200 p.p.m. or less of anisomycin, nystatin and actidione had little or no detectable effect on the Myxophyceae but were toxic to members of the Chlorophyceae and the Bacillariophyceae. Thus, these 3 antibiotics are of potential value in eliminating green algal and diatom contaminants from cultures of blue‐green algae. Since bacitracin was found to be inhibitory to members of the Myxophyceae at concentrations not toxic to representatives of the other groups tested, it may prove useful in eradicating blue‐green algae from cultures of other forms. Microscopic examinations indicated that the cells of cultures of species belonging to the Chlorophyceae, the Myxophyceae, and the Euglenophyceae, when exposed to antibiotics to which they were sensitive, usually underwent lysis, while those of species of Xanthophyceae and of Bacillariophyceae generally showed a loss in pigmentation.