MUTAGENESIS OF ANACYSTIS-NIDULANS BY N-METHYL-N'-NITRO-N-NITROSOGUANIDINE AND UV-IRRADIATION

Inactivation of the blue-green alga, Anacystis nidulans, with nitrosoguanidine was concentration-dependent. Nitrosoguanidine-induced mutation frequencies were: 1.8 · 10-3, 2.98 · 10[su-3], 3.7 · 10-3, 1.0 · 10-3 and 4.8 · 10-4 for yellow and blue, minute-colony-forming, filamentous or snake, and polymixin-B-resistant mutants, respectively. UV-irradiated damage within the experimental conditions utilized was completely photoreactivity by visible light. When a UV-irradiated culture was incubated in the dark for 9 h, a survival curve with slope k = -0.066 (where k = ln S S0 · t-1) was observed. A small shoulder was evident, and the extrapolation of the asymptote of the curve to the ordinate showed an inactivation number of 2. Minute-colony-forming and snake mutants were also induced by UV irradiation if photoreactivation was prevented. The inability to isolate auxotrophic mutants of Anacystis nidulans was considered to be due to intrinsic properties and therefore presents a major problem in blue-green algal genetics. © 1969.