CELL INACTIVATION, MUTATION AND DNA STRAND-BREAK INDUCTION BY GAMMA-RAYS AT VERY-LOW TEMPERATURES

Cell inactivation, mutation and DNA strand-break induction by gamma-ra diation have been investigated at very low temperatures (- 78 degrees C, - 196 degrees C, and -268 degrees C). In Escherichia coli Y-mel, la cI(+)-->lacI(-) and Salmonella typhimurium TA102, his(-)-->his(+) dose -modifying factors determined for low radiation doses are similar for both mutation induction and cell inactivation. The sensitivity of repa ir-deficient strains E. coli polA(-) and E. coli recA(-) was also redu ced at low temperature to a comparable extent. This suggests that the lesions which are responsible for cell inactivation and mutagenesis co uld be strongly mutually related and/or that different types of lesion s which are responsible for cell inactivation and mutation induction i n bacteria are reduced at low temperature to the same or similar exten t. Likewise, a lower yield of DNA strand breaks in plasmids irradiated at low temperature was observed.