Toxicity of Irradiated Medium for Repair-Deficient Strains of
            <i>Escherichia coli</i>

Webb, Robert B.; Lorenz, John R.

doi:10.1128/jb.112.1.649-652.1972

Cited by 42 publications

(6 citation statements)

References 7 publications

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“…Our results parallel those of Webb and J,orenz (4) who report that preirradiation of nutrient medium produces a toxicity associated with the genetic deficiencies fil, phr, and recA in E. coli. They also noted that uvr and other repair-sufficient strains of E. coli are not sensitive to preirradiated medium, that recA and fil strains are more sensitive to medium preirradiated with black light than visible light, although the phr mutant is very sensitive to medium preirradiated with visible light (4).…”

supporting

confidence: 91%

Toxicity of l -Tryptophan Photoproduct on Recombinationless ( rec ) Mutants of Salmonella typhimurium

Yoakum

Eisenstark

1972

J Bacteriol

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l -Tryptophan after exposure to black light becomes toxic for recombinationless ( rec ) mutants of Salmonella typhimurium . Fifty-six radiation-sensitive mutants were screened for sensitivity to the tryptophan photoproduct; the rec and exr (X-ray sensitive) mutants are sensitive, whereas the uvr, hcr , and wild-type strains are resistant. A number of catabolic products of tryptophan and compounds related to tryptophan were screened for toxicity to rec strain; these are nontoxic or far less toxic for rec strains than irradiated l -tryptophan. The toxic photoproduct is relatively stable to drying and basic hydrolysis at 90 C, indicating that it is a stable organic compound, eliminating peroxide as the toxic component. It was also observed that the toxic product is a photooxidation product since it is formed only when l -tryptophan is irradiated in the presence of air.

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supporting

confidence: 91%

Toxicity of l -Tryptophan Photoproduct on Recombinationless ( rec ) Mutants of Salmonella typhimurium

Yoakum

Eisenstark

1972

J Bacteriol

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“…The existence of a class of nonviable but residually dividing cells resolves the apparent discrepancy between the effects of rec mutations on growth rates versus viabilities: the intermediate class of cells contributes to the mass increase of the culture, but not to the viability. Furthermore, our results indicate that the inviability of Recstrains does not result from an increased sensitivity of these strains either to the manipulations associated with plating cells on solid medium or to possible chemical changes that may occur when agar medium is exposed to fluorescent room lighting (20).…”

Section: Discussionmentioning

confidence: 79%

“…Changes in ionic strength, temperature, and richness of medium do not affect viability, nor does the irradiation given off by fluorescent room lights during the growth of the cultures (4). It has been suggested that pre-irradiation of' the agar medium by fluorescent room lights may lower recAviability (20).…”

mentioning

confidence: 99%

Analysis of the Growth of Recombination-Deficient Strains of Escherichia coli K-12

1974

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Cultures of' recombination-deficient strains of Escherichia coli are composed of' three classes of cells: (i) viable cells, which can undergo 20 or more generations, (ii) residually dividing cells, which can undergo fewer than 20 generations (probably an average of' f'ewer than 6). and (iii) nondividing cells, which are incapable of' a single division. The nonviable but residually dividing cells contribute to the mass increase of the culture, but not to the viability, thus accounting for the apparent dissimilarity in the effects of' rec mutations on growth rates and viabilities. We have determined the frequencies of cells in each of' the three classes, and, by making a simplifying assumption concerning the relative division times of viable and residually dividing cells, we have been able to describe mathematically the growth of the rec-cultures.Strains of' Escherichia coli K-12 with lesions in either the recA, recB, or recC genes exhibit a variety of phenotypic alterations when compared with isogenic rec+ strains. recA mutants are characterized by high sensitivity to ultraviolet (UV) irradiation, sensitivity to X-irradiation, excessive deoxyribonucleic acid (DNA) breakdown, both during normal growth and after UV irradiation, low spontaneous production of lambda phage from lysogens, no detectable recombination prof'iciency in bacterial crosses, and alterations in cell division processes (9,11,14,21). recB and recC mutants are characterized by moderate UV sensitivity, sensitivity to X-irradiation, reduced DNA breakdown after UV irradiation, normal spontaneous production of' lambda phage f'rom lysogens, reduced recombination proficiency, and the absence of' an adenosine triphosphate-dependent deoxyribonuclease (exonuclease V) (1, 16. 19, 21). Strains carrying both a recA and a recB or a recC mutation retain the high sensitivity to UV irradiation and undetectable recombination proficiency characteristic of recA mutants, but have lost exonuclease V activity and no longer degrade their DNA excessively either during normal growth or after UV irradiation (21).In addition to the above defects, mutants with lesions in any of the three rec genes grow more slowly and have significantly lower viability than isogenic rec+ strains (4,8,9,22). Previously obtained data on the relative growth

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“…If BL damage is mediated by an endogenous photosensitizer (1), the chromophore involved must be highly specific for near-UV radiation since little inactivation by CW was observed. Several candidates for a near-UV chromophore have been proposed (13,25). That the BLinduced lethal lesions are not cyclobutyl pyrimidine dimers is suggested by the observation that PR does not enhance survival of N. crassa after BL irradiation (data not presented).…”

Section: Resultsmentioning

confidence: 99%

Inactivation of carotenoid-producing and albino strains of Neurospora crassa by visible light, blacklight, and ultraviolet radiation

Blanc¹,

Tuveson²,

Sargent³

1976

J Bacteriol

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Suspensions of Neurospora crassa conidia were inactivated by blacklight (BL) radiation (300 to 425 nm) in the absence of' exogenous photosensitizing compounds. Carotenoid-containing wild-type conidia were less sensitive to BL radiation than albino conidia, showing a dose enhancement factor (DEF) of 1.2 for dose levels resulting in less than 10%. survival. The same strains were about equally sensitive to shortwave ultraviolet (UV) inactivation. The kinetics of BL inactivation are similar to those of photodynamic inactivation by visible light in the presence of a photosensitizing dye (methylene blue). Only limited inactivation by visible light in the absence of exogenous photosensitizers was observed. BL and UV inactivations are probably caused by different mechanisms since wild-type conidia are only slightly more resistant to BL radiation (DEF = 1.2 at 1.0% survival) than are conidia from a UV-sensitive strain (upr-1, uvs-3). The BL-induced lethal lesions are probably not cyclobutyl pyrimidine dimers since BL-inactivated Haemophilus influenzae transforming deoxyribonucleic acid is not photoreactivated by N. crassa wild-type enzyme extracts, whereas UV-inactivated transforming deoxyribonucleic acid is photoreactivable with this treatment.

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Toxicity of Irradiated Medium for Repair-Deficient Strains of Escherichia coli

Cited by 42 publications

References 7 publications

Toxicity of l -Tryptophan Photoproduct on Recombinationless ( rec ) Mutants of Salmonella typhimurium

Toxicity of l -Tryptophan Photoproduct on Recombinationless ( rec ) Mutants of Salmonella typhimurium

Analysis of the Growth of Recombination-Deficient Strains of Escherichia coli K-12

Inactivation of carotenoid-producing and albino strains of Neurospora crassa by visible light, blacklight, and ultraviolet radiation

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