THE ACTION OF X-RAYS ON INTRACELLULAR 

 BACTERIOPHAGE FORMATION 



F. HERCIK 



Biojihysical Institute of the Czechoslovak Academy of Sciences, Brno, 



Czechoslovakia 



SUMMARY 



1. Inactivation of the capacity of E. coll B for phage T 3 by the action of soft 

 X-rays was measured. 



2. The dose-effect curve is biphasic. After small doses, rapid inactivation 

 occurred, but the inactivation was markedly slower after large doses. 



3. The capacity of irradiated E. coU B was affected by addition of chloram- 

 phenicol. On adding chloramphenicol to irradiated bacteria together with the 

 phage during the logarithmic phase, the decrease in capacity was relatively 

 smaller than might have been expected if the deleterious effects of the two 

 factors were cumulative. In stationary cultures the protective effect of chloram- 

 phenicol was less marked. 



The ability of bacterial cells to form phage was defined by Benzer 

 and Jacob (1953) as the capacity. Earlier observations by Anderson 

 (19J:4, 1948) showed that cells of Escherichia coli sterilized by large 

 doses of ultraviolet radiation could still form phage T4. Later it was 

 found that the capacity of E. coli for other phages was much more 

 sensitive to the action of ultraviolet radiation (Benzer, 1952; Garen 

 and Zinder, 1955; Labaw et al., 1953; Tessman, 1956). Similar results 

 were obtained with ionizing radiation (Rouyer and Latarjet, 1946; 

 Tobin, 1953; C4aren and Zinder, 1955; Pollard et al., 1958). Recent 

 measurements (Stent, 1958) have shown that, for phage T 2, a dose of 

 650,000 r is required to inhibit two-thirds of the bacterial phage-forming 

 capacity. 



A deeper insight into this remarkable phenomenon will not only 

 elucidate, to a certain degree, the mechanism of the basic action of 

 radiation on living matter but will also reveal the processes of phage 

 formation. 



In our laboratory the inactivation by X-rays of the capacity of E. 

 coli for phage T3 has been studied. The immediate effect of ionizing 

 radiation was compared with the delayed effect. In another series of 

 experiments the protein synthesis of the irradiated bacterial cells was 



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