An Observed ‘Oxygen Effect’ during Gamma-irradiation of Dried Bacterial Spores

Abstract

ON numerous occasions it has been shown that changes produced in aqueous biological systems by exposure to ionizing radiations of low specific ionization can be influenced by environmental conditions during irradiation. Since it is considered that environmental conditions affect the types and yields of free radicals formed on irradiation of water, the suggestion has been made that the observed biological changes are induced mainly by indirect action. Recent observations on irradiated non-aqueous synthetic macromolecular systems and on dry isolated cellular constituents have shown that changes produced by direct action can also be influenced by environmental conditions^1–3. Alexander⁴ has therefore postulated that direct action may cause changes in biological systems in cases where, in the past, it was thought that indirect action was responsible. However, alteration of the environmental conditions in circumstances where only direct action is known to be operative has not yet been shown to influence the lethal action of ionizing radiations on bacterial cells.