Radiation-Induced Mutagenicity and Lethality in Ames Tester Strains of Salmonella

Abstract

Mutation and killing induced by X radiation and 60CO gamma radiation were studied in six different histidine-requiring auxotrophs of Salmonella typhimurium. Strain TA100, which is sensitive to base-pair substitutions, and strains TA2637 and TA98, which are sensitive to frameshifts, carry the pKM101 plasmid and exhibit significantly higher radiation-induced mutations compared to their plasmidless parent strains TA1535, TA1537, and TA1538, respectively. Among the plasmid-containing strains, TA98 and TA2637 are much more sensitive to the mutagenic action of radiation than is TA100 based on a comparison with their respective spontaneous mutation rates; however, no uniformity was observed in the responses of the strains to the lethal action of ionizing radiation. The pKM101 plasmid provides partial protection against lethality in TA100 and TA2637, whereas the same plasmid enhances the lethal action of ionizing radiation in TA98. The following conclusions are consistent with these observations: (1) the standard Ames Salmonella assay correctly identifies ionizing radiation as a mutagenic agent; (2) frameshift-sensitive parent strains are more sensitive to the mutagenic effects of ionizing radiation than is the only strain studied that is sensitive to base-pair substitutions; and (3) enhancement of mutagenesis and survival is related to plasmid-mediated repair of DNA damage induced by ionizing radiation and does not involve damage induced by Cerenkov-generated uv radiation which is negligible for our irradiation conditions.

Evaluation of the Effects of Radiation from an X-ray Baggage Inspection System on Microbial Agents

“…Incubation in the presence of a mutagen causes a back mutation, restoring the wild type histidine operon, and results in histidine-independent colony growth which is then scored (Maron & Ames, 1983). In addition to testing chemical substances, the Ames test has also been used for screening the mutagenicity of ionizing radiation (Imray & MacPhee, 1981;Isildar & Bakale, 1984), ultra violet radiation (MacPhee & Schoeffel, 1981), and extralow-frequency radiation associated with electromagnetic fields (Moga & Obringer, 1996).…”

“…TA98 possesses a hisD3052 mutation in the hisD gene coding for histidinol hydrogenase with eight repetitive GC residues near the site of a -1 frameshift mutation (Isono & Yourna, 1974), while TA100 contains a mutation in the hisG46 gene coding for the first enzyme of histidine biosynthesis, in which an A-T in the wild type sequence has been substituted with a G-C, changing a proline to leucine (Barnes et al, 1982). These strains have been used previously for radiation-induced mutagenicity studies and have been found appropriate and sensitive to the mutagenic action of radiations (Imray & MacPhee, 1981;Isildar & Bakale, 1984. Detailed methods for conducting the Ames test have been published else-where (Maron & Ames, 1983;Mortelmans & Zeiger, 2000).…”

Le SOS chromotest : des cellules bactériennes pour détecter et caractériser produits et radiations génotoxiques

“…Toutefois, les résultats se sont avérés peu reproductibles entre différents laboratoires et, dans les conditions standard d'utilisation, la sensibilité est faible puisque les doses donnant une réponse mesurable sont de l'ordre de quelques dizaines à quelques centaines de grays [1,15,20]. Des modifications des souches [22] ou du protocole [35] ont permis d'obtenir des sensibilités de l'ordre de quelques grays.…”

Detection of radiation effects using recombinant bioluminescent Escherichia coli strains

“…Since the early 1980s, there have been several trials to monitor the effects of ionizing radiation on microorganisms using bacterial cells including the Ames test [1,2]. Before finally applying these methods, several limitations including detection time, detection methods, and sensitivity must be overcome.…”