Mutagenic action of heavy ions on Escherichia coli cells.

Induction of direct mutations in the lactose operon of E. coli cells by gamma-radiation and accelerated heavy ions with different LET was studied. The experiments were performed with the wild-type PolA and LexA strains. A quadratic dependence of the mutation rate on the dose of different radiations for the wild-type strain and the PolA mutant was observed. However, different types of radiation showed different relative genetic effectivenesses (RGE). The dependence of RGE on LET for the wild-type and PolA strain has a maximum. A LexA strain showed much reduced mutation rates and a linear dose response. The RGE decreased with increasing LET of ionizing radiation.