The use of antibiotics to obtain axenic cultures of algae

Abstract

Attempts to obtain undamaged axenic cultures of six algae by means of short-term exposure to various antibiotic mixtures were successful in four cases. Apparently pure cultures of the two diatoms, Nitzschia capitellata Hust. and Amphora coffeaeformis var. perpusilla (Grun.) Cleve were obtained after short exposure to penicillin + Ceporin + aureomycin, followed by mechanical separation. No changes in cytology or pigmentation and growth characteristics could be detected. Axenic Pediastrum boryanum (Turp.) Menegh. var. boryanum resulted after short exposure to penicillin + tetracycline + chloramphenicol + aureomycin; further addition of neomycin, Ceporin or streptomycin here effected no advantage, and 20·0 µg/ml neomycin was algicidal. For Chlorella vulgaris Beij. var. vulgaris, the addition of neomycin at 1·25–20·0 μg/ml to the 4-antibiotic mixture above was necessary to eliminate a yeast. The Tribonema viride Pasch. and Oscillatoria animalis J. Ag. cultures remained contaminated with Penicillium and bacteria; the antibiotic sensitivity patterns of the residual bacterial flora are given, and suggestions made for their elimination. The practical difficulties involved when trying to prove the absence of all bacteria are briefly discussed.