Isolation, growth and nitrogen fixation of a gas vacuole-less mutant of the blue-green alga Anabaena aphanizomenoides.

Mutants with loss of gas vacuoles (GVL-) were isolated from a clonal population of the gas vacuole containing (GVL+) blue-green alga Anabaena aphanizomenoides with a spontaneous mutation frequency of 1.7 x 10(-3) in nitrogen-free media. Growth and nitrogen fixation of the mutant were slow when compared to the GVL+ parent. Both the parent and mutant filaments tolerated 0.02 microgram/ml of streptomycin, and higher concentrations were lethal. The reversion of the mutant towards the parent did not occur.