The Lethal Effects of Alpha Irradiation on Wild-Type and on a High-Catalase Mutant of Rheudopseudomonas spheroides

Abstract
Wild type Rhodopseudomonas spheroides and a high-catalase mutant were studied with regard to the lethal actions of a-particles from radon and of reagent H2O2. The catalase of the mutant affords marked protection against H2O2 but not against a-particles. The killing by a-irradiation was not changed materially by altering the cell suspension density or by the presence of oxygen during irradiation. Application of target theory indicates that a cell loses viability if any part of it is intersected by the track of an a-particle. Exposure of wild-type R. spheroides cells to externally applied 1 M H2O2 for 30 seconds reduces the viable count by 50%. It is concluded that H2O2 in its ground state does not play a significant part in mediating the lethal action of a-particles on R. spheroides.

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