Heavy ion inactivation in Escherichia coli cells: experiment and theory

Cross sections for inactivation of stationary cells of E. coli strains (B(s-1) and B/r) by heavy ions (Z = 8-92) with energies <15 MeV/u were determined from survival curves and compared with track structure calculations. Whereas for low energies, inactivation cross sections for both strains are similar, and thus do not reflect their difference in X-ray sensitivity, the ratios of cross sections of the two strains approach the ratio of X-rays sensitivities for heavy ions at high energies. The essential features of the experimental data are reproduced well by the track structure calculations, which do not use fitted values for the model parameters but independently determined values for the X-ray sensitivities and the size of the target structure. Quantitatively, the calculations underestimate the cross sections for heavier ions as well as their ratios at higher energies. Some possible reasons for these discrepancies are discussed.