MUTATION-INDUCTION BY ACCELERATED HEAVY-IONS IN BACTERIA

Induction of lacI(-) forward mutations in Escherichia coli Y-mel and h is(-) --> his(+) reversions in Salmonella typhimurium TA102 was invest igated after irradiation with heavy ions in the range of Z = 1-36. Par ticle specific energies (E) were in the range of 1-600 MeV/u. A strong dependence of the mutation induction cross-section (sigma(m)) on both particle energy and LET(infinity) was observed. The results suggest t hat two different ranges of LET(infinity) can be distinguished. In the range of high LET(infinity) (>100 keV/mu m) sigma(m) increases with i ncreasing specific particle energy if LET(infinity) is kept constant ( Fe ions as compared with carbon ions or alpha-particles). In the range of low LET(infinity) (<100 keV/mu m) sigma(m) decreases with increasi ng energy (Ne ions as compared with He ions).