CHEMICAL MUTAGENESIS IN E COLI B/R - INFLUENCE OF REPAIR SYSTEMS FOR UV DAMAGE

Broth-grown cells of the Escherichia coli B/r try- auxotroph WWP-2 exhibit the following properties when treated with ultraviolet light, di-epoxybutane or nitro-somethylurethane. Late lag phase cells show, after ultraviolet-irradiation, a strong influence of caffeine upon survival and revertant frequencies. There is also a large enhancement of revertant frequencies in the presence of an amino acid pool. No such effects are found for di-epoxybutane or nitrosomethylurethane-treated cells. There is, however, a weak synergistic effect of caffeine plus an amino acid pool on di-epoxybutane-induced revertant frequencies. Stationary phase cells show decreased survival and increased revertant frequencies, after ultraviolet irradiation, when platings are made on minimal medium, plus a low level of tryptophan, supplemented with caffeine. There is a weak enhancement of revertant frequencies by enrichment of the low tryptophan medium with an amino acid pool. When caffeine is combined with the amino acid pool there is a greater than additive enhancement of revertant frquencies. Caffeine and an amino acid pool are, individually, without obvious effect on survival or revertant frequencies obtained following treatment with nitrosomethylurethane or di-epoxybutane. For cells treated with di-epoxybutane there is a weak synergistic effect of caffeine plus an amino acid pool on revertant frequencies. © 1966.