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.