Summary
1. The radiosensitivity of cultures resistant to 1500 iu/ml, 2000 iu/ml, 2500 iu/ml of penicillin, produced from strain E. coli B was examined.
2. Cultures in the log-phase were streaked in monocellular layers on the agar surface and exposed to x-irradiation.
3. As a result of penicillin treatment cell-filaments consisting of several segments were formed.
4. Measurement of viability of x-irradiated cultures proved that penicillin resistant cultures are considerably more radioresistant than the parent strain B, non-treated with penicillin.