Inactivation of bacterial spores by charged particles.

谷 田貝文夫,高 橋 旦,北 島淑男,松 山 晃:理 化学研究所,埼 玉 県和光市広沢2-1 〒351 Bacillus subtilis spores were bombarded with ƒ¿-particles and heavy ions of carbon , nitrogen, and oxygen accelerated in the IPCR cyclotron. The maximum RBE was found at an unrestricted LET of about 120 keV•EƒÊm-1 The effective inactivation cross section, Seff, for ƒ¿-particles increased with LET, reaching a stationary level of Sƒ¿st, 0.145 ƒÊ2. The analysis of the LET dependence revealed that seve ral primary activations are required for producing one lethal-hit, within a very short length of the particle track. The value of Sƒ¿st was lower than Seff for heavy ions (0.22-0.26 ƒÊm2). This discrepan cy may be due to a difference of the repair capacities of "strand-target" between ƒ¿-particles and heavy-ion bombardments, or to existence of a target (s) which is sensitive for bombarding particles of extremely high LET, or to a long-range effects caused by such high-LET particles.