Radiation sensitivity of N. pharaonis in comparison with E. coli K12 strains.
To investigate the radiation sensitivity of the natronobacterium Natronomonas pharaonis in comparison with Escherichia coli strains (N. pharaonis DSM 2160T, E. coli strains AB1157 and K12 lambda s) were exposed to gamma-radiation (60Co-gamma-source, 100 Gy min-1) in the presence of oxygen (air) and under strongly reduced oxygen conditions (argon-saturated medium). After irradiation, the colony-forming ability (dose-survival curves) and the D37 dose were determined. The oxygen content of the solutions containing high NaCl concentrations was measured with an oxygen electrode (Clark electrode). It was found that N. pharaonis can tolerate a remarkably higher irradiation dose than the two E. coli strains (approx. 1.5-fold of K12 lambda s and approx. 4-fold of AB1157). The oxygen enhancement ratio (OER) is 2.8 for N. pharaonis and 2.6 for both E. coli strains. Therefore the higher radiation resistance of the N. pharaonis is not due to the low oxygen content of the cell solution (high salt concentration) but is probably related to the higher DNA repair ability of this archaebacteria strain.
Institute for Theoretical Chemistry and Structural Biology, University of Vienna, UZA II, Althanstrasse 14, 1090 Vienna, Austria. ruth.quint@univie.ac.at
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D002460:Cell Line; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D004926:Escherichia coli / Q000145:classification / Q000378:metabolism* / Q000528:radiation effects*; D005720:Gamma Rays; D019633:Natronobacterium / Q000145:classification / Q000378:metabolism* / Q000528:radiation effects*; D010100:Oxygen / Q000378:metabolism*; D011829:Radiation Dosage; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013045:Species Specificity
D003037:Cobalt Radioisotopes; D010100:Oxygen