Isolation of gas vacuole-less mutants of the blue-green alga Anabaenopsis raciborskii

From a bloom forming blue-green alga, Anabaenopsis raciborskii, spontaneous mutants, which had lost the ability to form gas vacuoles have been isolated; the mutant frequency was 4.8×10^-3. The filaments of gas vacuole-less mutants settled at the bottom of flasks in liquid culture media unlike the parent alga. The growth and nitrogen fixation were comparatively poor in the mutants.