INTERPRETATION OF MUTATION-INDUCTION BY ACCELERATED HEAVY-IONS IN BACTERIA

In this report, a quantitative interpretation of mutation induction cr oss sections by heavy charged particles in bacterial cells is presente d. The approach is based on the calculation of the fraction of energy deposited by indirect hits in the sensitive structure. In these events the particle does not pass through the sensitive volume, but this reg ion is hit by delta rays. Four track structure models, developed by Ka tz (in Quantitative Mathematical Models in Radiation Biology, pp. 57-8 3, Springer-Verlag, 1988), Chatterjee et al. (Radiat. Res. 54, 479-494 , 1973), Kiefer and Straaten (Phys. Med. Biol. 31, 1201-1209, 1982) an d Kudryashov et al. (Proceedings of the First Soviet Congress on Micro dosimetry, Atomizdat, Moscow, 1973), respectively, were used for the c alculations. With the latter two models, very good agreement of the ca lculations with experimental results on mutagenesis in bacteria was ob tained. Depending on the linear energy transfer (LET(infinity)) of the particles, two different modes of mutagenic action of heavy ions are distinguished: ''delta-ray mutagenesis,'' which is related to those ra diation qualities that preferentially kill the cells in direct hits (L ET(infinity) greater than or equal to 100 keV/mu m), and ''track core mutagenesis,'' which arises from direct hits and is observed for light er ions or ions with high energy (LET(infinity) less than or equal to 100 keV/mu m). (C) 1995 be Radiation Research Society