Comparative mutagenesis of Escherichia coli strains with different repair deficiencies irradiated with 222-nm and 254-nm ultraviolet light.
Photoinactivation and reversion to tryptophan prototrophy were studied in four Escherichia coli strains with different repair deficiencies. Cells were irradiated with 222-nm wavelength UV emitted by an excimer lamp and with 254-nm wavelength UV emitted by a low-pressure mercury lamp. Strain DSM 9494 (trp(-)uvrA(+)) turned out to be most resistant while the strain DSM 9495 (trp(-)uvrA(-)), which is defective in nucleotide-excision repair (NER) was most sensitive to both wavelengths. UV-fluence rates for a respective inactivation were twice as high for 222-nm wavelength UV than for 254-nm UV. No clear difference in efficiency of inactivation could be observed between the two wavelengths in strains DSM 9496 (trp(-)uvrA(+) pKM101) and DSM 9497 (trp(-)uvrA(-) pKM101). In general, more revertants were induced by 254-nm wavelength UV, which corroborates the hypothesis that a higher amount of DNA damage was induced by this wavelength than by 222-nm UV, except for DSM 9497 where no clear difference could be observed regarding the number of revertants induced by both wavelengths. This strain DSM 9497 has a high sensitivity to certain oxidative mutagens compared with other strains, which is indicative of formation of reactive oxygen species during irradiation with 222-nm wavelength UV.
Clauss
Marcus
M
Faculty of Biology, University of Bielefeld, Universitätsstrasse 25, 33615 Bielefeld, Germany. marcus.clauss@uni-bielefeld.de
Grotjohann
Norbert
N
D004260:DNA Repair / Q000235:genetics* / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects*; D005838:Genotype; D016296:Mutagenesis / Q000502:physiology* / Q000528:radiation effects; D011836:Radiation Tolerance / Q000235:genetics; D014466:Ultraviolet Rays