Lethal effect of K-shell absorption of intracellular phosphorus on wild-type and radiation sensitive mutants of Escherichia coli.

The present study was conducted to clarify the lethality of Auger cascades induced by the K-shell photoabsorption of phosphorus in Escherichia coli. Killing of wild-type and radiation-sensitive mutants of E. coli was examined. Three x-ray energies were chosen for irradiation; at 2.153 keV: the resonance peak of K-shell photoabsorption of phosphorus; at 2.146 and 2.160 keV: off-peak. Enhancement ratio, which was defined as the ratio of the killing sensitivity of 2.153 keV to that at 2.146 keV, were 1.32 to 1.54 for examined strains. Increment of absorbed energy calculated in entire cells for 2.153 keV radiation could not explain the degree of observed enhancement of killing. Lethality of Auger cascades depended on the killing sensitivity with x-rays which did not induce Auger cascades. The lethality for wild-type was lower than that for recombination repair-deficient mutants. It was concluded that one part of damages produced by Auger cascades was repaired in wild-type strains.