Abstract
The process whereby bacterial cultures are alternately grown and then irradiated ([gamma] -radiation) through several ''cycles'' was studied as a means of developing radioresistant cultures of E- coli I. The nature of the environment at the time of irradiation influenced the extent of development of radioresistance. Radioresistance development was higher when the bacteria were irradiated in an organic environment than in an inorganic environment. Radioresistant mutants are probably not produced in high numbers by this type of process during a dose-fractionation procedure of food irradiation.