Inactivation of individual Bacillus subtilis spores in dependence on their distance to single accelerated heavy ions.

In order to understand radiation mechanisms of heavy ions in detail, it is necessary to study effects of single ions on individual biological test objects. Spores of Bacillus subtilis have been used as a suitable small biological test system to measure the inactivation in dependence on the radial distance to the tracks of charged particles. Accelerator experiments have been performed using a modified Biostack technique--biological objects sandwiched between nuclear track detectors. Results of these experiments using ions differing in their energy and atomic number will be discussed under following aspects: (i) methodological differences between the experiments and their possible influences on the results, (ii) common features which are independent on the particle type and energy, (iii) theoretical expectations and problems to find solid theoretical concepts which explain the results.