Apparent absence of relationship between repair of single strand breaks in DNA and gamma radiation resistance in Salmonella thompson.

Abstract

0736 01 1. A mutant strain of Salmonella thompson (S. thompson/r), with an increased resistance to gamma radiation, did not appear to possess a DNA repair system, active in a “non-growth” medium, similar to that reported for Micrococcus radiodurans and Escherichia coli B/r. 2. DNA strand breaks occurred to a similar degree in both the sensitive parent strain and the resistant mutant strain during exposure to gamma radiation. 3. The DNA could be reconstituted in both strains, but only when the cells were incubated in a growth-promoting medium after irradiation. 4. Results indicated that inactivation of S. thompson by gamma radiation was not the result of the production of DNA single-strand breaks per se, and the resistance of the mutant strain, therefore, did not appear to be directly related to the ability to repair such breaks.