Modification of Sensitivity to X-Irradiation by Water in Bacillus megaterium

Electron Beam Irradiation Dose Dependently Damages theBacillusSpore Coat and Spore Membrane

“…De Lara et al [10] also noted the need for at least 10 kGy of EBI to inactivate spores (in foodstuffs). The altered spore surface features we report indicate that free radicals derived from the water vehicle (H atoms and OH radicals, according to Tallentire and Powers [39]) likely attacked the spores from the outside. Damage leading to membrane failure and the resulting DNA degradation at the lower EB doses appear to have resulted from EB-induced free radicals within the spores, although this is yet to be determined.…”

“…EBI results in the direct chemical alteration of atoms resulting from energy capture [15, 16, 31] and the expulsion of electrons from atomic orbitals, altering electrically neutral atoms or molecules into charged free radicals [8, 37]. Damage caused by radiation-induced radical formation is affected primarily by spore water content and the presence of oxygen, the latter being required for maximal reduction in spore viability [38, 39]. Interestingly, spore radiation sensitivity is reduced at very low water content (such as at vapor pressures approaching ambient air); yet, radiation sensitivity is increased in spores suspended in water [39].…”

“…Damage caused by radiation-induced radical formation is affected primarily by spore water content and the presence of oxygen, the latter being required for maximal reduction in spore viability [38, 39]. Interestingly, spore radiation sensitivity is reduced at very low water content (such as at vapor pressures approaching ambient air); yet, radiation sensitivity is increased in spores suspended in water [39]. This sensitizing effect is due to the production of radiolytic products of water in the presence of oxygen—in particular, hydrogen peroxide and hydroxyl radicals [40].…”

(Symposium on Bacterial Spores: Paper VII). Recovering Spores Damaged by Heat, Ionizing Radiations or Ethylene Oxide

“…Observations that spore radiation damage may be modified by certain gases, by thiourea or by heat during storage (Tallentire & Powers, 1963;Powers & Tallentire, 1968) suggest that more attention should be paid to storage of spores before counting. Occasionally there are reports that counts of spores increase upon storage in less well-defined systems than those mentioned above.…”

Hydroxyl Radical and the Hydrated Electron in Radiation Effects in Cells.

“…The first complete study of the role of water in the spore was described by Tallentire and Powers (1963).…”