Action of mutagenic chemicals on Anacystis nidulans. III. N-methyl-N'-nitro-N-nitrosoguanidine

Abstract

The tolerance of the unicellular blue-green alga Anacystis nidulans to nitrosoguanidine increased from an initial level of 5 µg NTG/ml to 20 µg/ml during the course of 10 successive transfers in NTG-supplemented medium. Single treatments of log-phase cells with NTG at pH 5-6 resulted in a significant increase in the frequency of streptomycin-resistant mutants but only a marginal increase in the frequency of ultraviolet-resistant mutants was observed following single or 10 successive treatments with NTG. Attempts to score mutants resistant to penicillin, aminotriazole or NTG were unsuccessful since these agents failed to effectively kill or bleach the sensitive background population on the agar plates.