The temperature dependence of cellular radiation sensitivity as a method of investigating mechanisms of inactivation

Bacteria, at temperatures in the range from 60C to 430C, were exposed to intense pulses of 450 keV electrons from a field emission accelerator or to cyclotron-produced 24 MeV 3He++ particles degraded by 0.025 mm or by 0.15 mm thick aluminium foils. The bacteria were plated in thin aqueous layers on membrane filters for all of the irradiations and equilibrated with humidified gases. For the irradiations by electrons, with cells in nitrogen, survival decreased with increasing temperature over the whole range. A similar response was measured for cells in nitrogen or air that were exposed to 3He++ particles degraded by the thicker foil. There was no temperature dependence with the thinner foil. These results can be interpreted as a demonstration that different processes are involved in the inactivation of cells: one of these may be a cooperative type of interaction. (author)