OXYGEN AND NITRIC OXIDE AS MODIFIERS OF RADIATION INJURY IN SPORES OF BACILLUS MEGATERIUM

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Abstract
Dry spores of Bacillus megaterium when irradiated in the presence of oxygen, demonstrate maximum sensitivity. A 30% reduction in sensitivity is shown when irradiation in nitrogen is followed immediately by exposure to oxygen. Sensitivity observed in nitrogen can be halved by post-irradiation exposure to nitric oxice prior to exposure to oxygen. Radiation apparently forms long-lived free radicals which combine with oxygen to form irreversible lethal substances (Class HI damage), and nitric oxide removes these radicals. The sensitivity is 20% higher with irradiation in NO than that seen when NO is given after irradiation. The action of O2 and NO is the quenching of luminescence that conserves energy within the spore with a corresponding increase in damage.