Action of X-Irradiation on E. coli

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Abstract
Inhibition of colony forming abilities of X-irradiated Escherichia coli was tested for both in the wet and in the dry condition. Wet irradiations were done in phosphate buffer at pH 7.00. For dry irradiation drops of phosphate buffer suspension of bacteria on thin film of gelatin were dried in a vacuum desiccator for 48 hours. The radio-resistance of E. coli reached a saturation value after 24 hours of desiccation. The 37% survival doses were 3.6 Kr in wet and 12.4 Kr in dry condition. From the difference of the target volumes in the 2 conditions, the mean diffusion distance of the radicals formed by ionizing radiation in the fluid surrounding the target was calculated to be only a small fraction of the target dimension. This mean diffusion distance decreased if the number of targets per cell was more than one.