An unusual mutant affecting the frequency of organelle mutation

A mutant of Euglena gracilis Z is described that spontaneously produces irreversibly bleached mutants at a high frequency. Bleaching only occurs during exponential growth under highly aerobic conditions. The kinetics for bleaching and growth of bleached and nonbleached cells suggest that mutation is induced by segregation of a cellular component that becomes limiting after several culture generations. The properties of spontaneous bleaching closely resemble the properties of induced organelle mutagenesis in E. gracilis and yeast.