Synergism and antagonism between N-methyl-N'-nitro-N-nitroso-guanidine and 9-aminoacridine in mutation induction in Escherichia coli K12.

When bacteria were treated simultaneously with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and low concentrations of 9-aminoacridine (9AA), the yield of frameshift mutations was much greater than that expected on the basis of independent action of both mutagens. In combination with a high concentration of 9AA, however, MNNG had an antagonistic effect upon the induction of frameshift mutations. There was no synergistic interaction between the two mutagens in bacteria in which the adaptive response to methylating agents had been induced. 9AA not only induced frameshift mutations, but also caused a small increase in reversions of a nonsense (ochre) mutation and, in combination with low MNNG concentrations, it had a small synergistic effect.