A Method for Producing, Selecting, and Isolating Photosynthetic Mutants of Euglena gracilis

A method was developed for the isolation of photosynthetic mutants of Euglena gracilis. It consists of the following steps. (a) Incubation of the cells under phototrophic conditions in the presence of 3 (3,4-dichlorophenyl)-1, 1-dimethylurea for 1 week. This step caused a drastic reduction in the number of chloroplasts per cell; (b) mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine; (c) phototrophic growth for a few days to allow for phenotype expression; (d) selection by incubation in the presence of arsenate under phototrophic conditions for 2 days; (e) plating and growth under photoorganotrophic conditions; (f) assay of green colonies for ability to evolve oxygen. About 10% of the green colonies were found to be deficient in their ability to evolve oxygen. In principle the method may prove suitable for the isolation of other types of mutants of Euglena.