A Euglena Mutant Resistant to N-Methyl-N-Nitroso-p-Toluenesulfonamide

SYNOPSIS. Treatment of Euglena gracilis strain Z with N-methyl-N-nitroso-p-toluenesulfonamide (MNTS) produced a mutant (designated MNTS-40A) showing 2.5-fold greater resistance to the killing effects of MNTS and 40-fold greater resistance to “bleaching” by MNTS. The mutant destroyed MNTS 2–3 times faster than strain Z. As a consequence the nucleic acids of strain 40A became methylated to a smaller extent than those of Z. Strain MNTS-40A was net cross-resistant to either N-methyl-N'-nitro-N-nitrosoguanidine or ultraviolet light.