Growth Inhibitors and their Antagonists as Mutagens and Antimutagens in Escherichia coli

Abstract

Thirty-five substituted benzimidazoles, benzotriazoles and quinoxalines were tested as growth inhibitors on three mutants of Escherichia coli, strain W, having different purine requirements and on the ciliate Tetrahymena geleii. A number of the compounds, especially those with a nitro group in the benzene ring, were inhibitory. Both organisms were affected in a similar way by the compounds. Several of these analogues were tested for mutagenic activity a t the purine and streptomycin loci in a purine-requiring mutant of E. coli. Only inhibitory compounds were found to be mutagenic ; non-inhibitory concentrations of one analogue, 4-nitrO-6-hydroxybenzimidazole (NHB), were, however, also mutagenic. No specific mutagenesis was demonstrated. NHB was found to increase the rate of mutation as determined by the papilla method. Evidence is presented which eliminates the hypothesis that selection rather than mutagenesis was involved. This analogue did not increase the frequency of mutants in non-dividing cells, and was not incorporated into bacterial DNA. The mechanism of this mutagenesis is thought to include the inhibition of enzymes concerned with DNA synthesis. DNA and RNA and their constituents, purine and pyrimidine precursors and analogues, vitamin B,, and other vitamins, were found to have no effect on the inhibition or mutagenesis produced by NHB. Several amino acid combinations and one non-mutagenic analogue, 4-hydroxy-6-nitrobenzotriazole, were, however, found to interfere with mutagenesis by NHB. These compounds did not affect the frequency of spontaneous mutants. The amino acid combination was effective only when present simultaneously with the mutagen and did not act by a selection mechanism. The mechanism of antimutagenesis by amino acids may involve their ability to increase the growth rate and also to modify the inhibited nucleic acid metabolism. The mutagenesis by 5-nitroquinoxaline, a pterin analogue, was also found to be depressed by amino acids in the same purine-requiring mutant. The annulment of mutagenic activity by amino acids was strain and mutagen specific. Twenty-five known inhibitors of nucleic acid synthesis and antagonists to inhibition were tested for mutagenic activity in five strains of Eschmichia coZi. Several, including 6-mercaptopurine, were found to be mutagenic ; in addition, NHB, 5-nitroquinoxaline and 5-aminouracil were mutagenic in most of the strains tested. The mutagenic activity of 5-aminouracil was not annulled by thymine, thymidine or other nucleic acid components, but the mutagenesis of 6-mercaptopurine was annulled by purine bases and by ribosides.

“Mutational Synergism” of Ultraviolet Light and Caffeine in Escherichia Coli

“…It is conceivable that these differences in cell treatment might alter the incorporation of the analogue. Greer (1958) observed that 250 Ag/ml had on effect on the growth rate or the spontaneous mutation rate from auxotrophy to prototrophy in E. coli. Witkin (1958), however, postulated that the increased mutagenesis was due to an inhibition of DNA synthesis by caffeine, allowing more time for "promutants" to become mutants before the start of DNA synthesis.…”

Advances in the Study of Respiration-Deficient (Rd) Mutation in Yeast and Other Microorganisms1

“…However, there is still a possibility that effective and versatile anticancer drugs may be finally discovered as examples of the mutagen-antimutagen relationship. In fact, some mutagens are counteracted by structurally analogous agents as seen in caffeine and theophylline versus adenosine and guanosine (92), and 4-nitro-6-hydroxybenzimidazole versus 4-hydroxy-6-nitrobenzotriazole (33). Furthermore, the "counteractive interference" between some mutagens for bacteria as well as some RD inducers for yeast (see Section IV-C) makes the prospect somewhat brighter.…”

Effect on the Offspring of Repeated Caffeine Administration to Pregnant Rats

“…Since caffeine is a universal beverage and is consumed in large quantities by the human race, its effect during gestation on the developing offspring is important. There is good evidence that caffeine is mutagenic in bacteria (Demerec and his co-authors, 1950;Demerec, Bertani & Flint, 1951;Gezelius & Fries, 1952;Novick, 1955;Greer, 1968), fungi (Fries, 1950;Zetterberg, 1959) and plants (Kihlman & Levan, 1949;Kihlman, 1952), as well as in Drosophila (Andrew, 1959;Ostertag, 1963;Ostertag & Haake, 1966;Mittler, Mittler & Owens, 1967) and in human cells in vitro (Ostertag, Duisberg & Stürmann, 1965;Ostertag, 1966a, b;Ostertag & Greif, 1967). Although there have been some conflicting reports on the mutagenicity of caffeine in higher organisms (Adler, 1970;Epstein, 1970), chromosomal breakage has been induced in human cell cultures as well as in Drosophila (Kuhlmann, Fromme, Heege & Ostertag, 1968).…”