Induction of axenic culture of Arthrospira (Spirulina) platensis based on antibiotic sensitivity of contaminating bacteria.

Arthrospira platensis SAG 21.99 and the isolated bacteria (Halomonas spp., Staphylococcus sp., etc.) from the culture of A. platensis SAG 21.99 were treated with five antibiotics to determine the minimal lethal concentrations. The combination of a washing step and a consecutive treatment with antibiotics, imipenem (100 microg ml(-1)), neomycin (100 microg ml(-1)) and cycloheximide (20 microg ml(-1)), treatment step was highly effective in eliminating bacteria. An axenic culture of A. platensis SAG 21.99 could be induced within 3 days using this method. This technique is a simple and rapid method for obtaining axenic cultures of filamentous cyanobacteria.