Photoreversal of ultraviolet-induced mutagenic and lethal effects in Escherichia coli

Effects of near-ultraviolet irradiation on growth and oxidative metabolism of bacteria

Kashket, E. R. (Harvard Medical School, Boston, Mass.) and A. F. Brodie. Effects of near-ultraviolet irradiation on growth and oxidative metabolism of bacteria. J. Bacteriol. 83:1094-1100. 1962.-The effects of irradiation with near-ultraviolet light (360 mmu) have been studied with Escherichia coli W and a strain of Pseudomonas aeruginosa. The growth of the aerobe P. aeruginosa was inhibited by light on minimal salts media containing succinate, glutamate, or glucose as sole carbon sources. The facultative anaerobe E. coli was capable of growth under irradiation on a fermentable carbon source, such as glucose, but with a smaller yield of cells on limiting substrate, as compared to unirradiated control cultures. The rate of growth of aerobic irradiated cells on glucose was equal to that of anaerobic growth on that carbon source, and there was a greater accumulation of end products of glucose catabolism aerobically in the light as compared to dark controls. When irradiated in media containing carbon sources from which energy was obtainable only by oxidative phosphorylation, such as succinate or malate, E. coli cells were still capable of oxidizing these substrates but could not grow on them. This bacteriostatic effect of 360-mmu light could be reversed by the addition of glucose, which resulted in the growth of irradiated cells. Visible (400 to 600 mmu) light was found to have no effect. Irradiated E. coli cells in succinate were found to contain no naphtho- or benzoquinones, compounds which are more sensitive to 360-mmu irradiation than other components of the respiratory chain. It is suggested that the effect of 360-mmu light on whole cells is the destruction of light-sensitive components, such as the benzoquinone Q(8) and naphthoquinone K(2)C(45) of E. coli W, which are essential for obtaining energy from oxidative metabolism.

Ultraviolet mutagenesis in bacteriophage T4. II. Photoreversal of mutational lesions

Drake, John W. (University of Illinois, Urbana). Ultraviolet mutagenesis in bacteriophage T4. II. Photoreversal of mutational lesions. J. Bacteriol. 92:144-147. 1966.-T4r mutations were induced by ultraviolet irradiation of extracellular phage particles, using a phage mutant, v, which is particularly susceptible to photoreactivation. Most of the induced r mutations could be subsequently photoreversed intracellularly with white light. Ultraviolet irradiation induces both transitions and sign mutations, and both were susceptible to photoreversal. The results suggest that two very different types of mutational lesions may arise from a common type of photochemical lesion.