72 



F. HERCIK 



therefore, to be expected that chloramj^henicol would influence the 

 production of phage in irradiated bacterial cells. 



The action of chloramphenicol on the capacity of irradiated E. coli 

 was studied in two series of experiments. In the first series, the chlor- 

 amphenicol was added to the irradiated bacteria at the time of in- 

 fection with the phage, or 15 min later at the end of the latent period. 

 Bacteria were infected for the determination of the capacity immedi- 

 ately after irradiation or 22 hr later. In the second series of experiments 

 the irradiated bacteria were exjDosed to the action of chloramphenicol 

 for different times before determining the capacity. 



10' 



10' 



> 



Capacity 



Nzch/Nch(3,0) 



Nzch/N,H(22,0) 



N 



Nzch/Nch(22,l5) 



_L 



24 



48 

 Dose (r) 



96x10' 



Fig. 2. — Relationship between capacity of E. coli B for phage T 3 in the presence of 

 cliloraniphenicol after irradiation with X-rays. 



Nch — capacity of non-irradiated bacteria treated with chloramphenicol. 



Nzch — capacity of irradiated bacteria in the joresence of chloramphenicol. 



Numbers in brackets : the age of culture in hours and the time in minutes at which 

 chloramphenicol was added. 



The toxic effect of chloramphenicol on the capacity of E. coli B was 

 investigated without previous irradiation. It was stated that the 

 addition of chloramphenicol during the logarithmic phase caused a 

 marked reduction of capacity (222-fold), while during the stationary 

 phase the reduction in capacity was about tenfold. 



Under these circumstances the combined effect of chloramphenicol 

 and radiation is bound to be manifested in a further decrease of the 

 capacity. In general it may be stated that in the presence of chloram- 

 phenicol the capacity of the bacteria decreased with the radiation dose, 



