INTRACELLULAR BACTERIOPHAGE FORMATION 73 



and that the biphasic character of the dose-effect curve was maintained. 

 Very interesting results are found when the data are plotted in such a 

 way that the capacity of irradiated and chlorani])henicol-treated cells 

 is compared with non-irradiated cells treated with chloramphenicol. 

 The effect of irradiation on the capacity was lowest in the 3-hr culture 

 to which chloramphenicol was added, together with the phage, immedi- 

 ately after irradiation. It has already been stated that the chloram- 

 phenicol itself has a high toxic effect; it would, therefore, be expected 

 that heavy irradiation doses would lead to complete inactivation of the 

 cai^acity. This is evidently not the case (see Fig. 2), and chloramphenicol 

 must, therefore, have a restorative effect. 



These experiments have clearly shown that chloramphenicol and 

 radiation do not supplement one another in inhibiting the capacity of 

 E. coli B to sustain phage growth but that under certain conditions 

 they can be antagonistic to each other. 



This problem was investigated in a second series of experiments with 

 the aim of diminishing the toxic effect of cliloramphenicol. The method 

 of Gillies and Alper (1959), using cellophane carriers on which the 

 bacterial culture was spread, was used. This method enabled us to 

 remove the carriers, after certain time intervals, from the surface of the 

 agar medium containing chloramphenicol. In these experiments, which 

 have not yet been completed, it can be shown that a short stay of 

 heavily irradiated cells (80,000 r) on chloramphenicol agar increases the 

 capacity ofE. coli for phage T 3. 



It is quite possible that this favourable effect is due to the fact that 

 chloramphenicol inhibits protein synthesis, and as the polymerization 

 of nucleic acids is also inhibited, a certain amount of DNA precursors 

 are accumulated, which can be used for restoration. 



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