Possible long range effects in the inactivation of bacterial cells by heavy ions

Inactivation of B. subtilis spores and E. coli B/r log-phase cells by heavy ions and α-particles has been investigated comparing with that by γ-rays. The survival curves of B. subtilis spores for γ-rays are almost exponential, but those of E. coli B/r show a shoulder which disappears depending upon the incubation condition. Inactivation cross sections are derived from analysis of the survival curves determined for different charged particles. To interpret the survival curves and cross sections, we have applied Katz's theory, track segment method and Oda's theory. Since analyses based on the latter two theories have already been made, analytical method based on the Katz's theory is described in some detail. Careful examination of the results shows that each of the three theories has some difficulties in interpreting the experimental results. Long range effects of heavy ions may be some of the causes for such difficulties. Possible causes of the long range effects are discussed. (author)