Method for isolation and purification of cyanobacteria.

A method employing nutrient saturated glass fiber filters allowed the isolation of the same numbers of cyanobacteria from freshwater as were obtained with medium solidified with agar, while providing a 2- to 15-fold reduction in the number of accompanying heterotrophic bacteria. Imipenem, a broad-spectrum beta-lactam antibiotic which inhibits peptidoglycan biosynthesis, was superior to some other beta-lactam antibiotics for reducing the numbers of heterotrophic bacterial contaminants associated with freshly isolated cyanobacteria to a level which facilitated the production of axenic cyanobacterial cultures.