The directed evolution of radiation resistance in E. coli.

E. coli AB1157 (a wild-type, K-12 strain having no known defects in DNA repair capability) was irradiated daily with a very large X-ray dose to develop a series of strains unusually resistant to both X rays and ultraviolet (UV) photons. An understanding of how wild-type strains mutate and become more resistant should lead to a better understanding of DNA repair processes and their effects on radiation sensitivity.