38. BIOSYNTHESIS OF PROTEINS IN BACTERIAL CELLS 437 



ence of chloramphenicol, the mucopeptides of the cell wall and probably 

 some protein of the cell membrane are still elaborated. 87 This may account 

 for the residual incorporation of radioactive amino acid into the protein 

 fraction after treatment with the inhibitor. 



The RNA and the DNA accumulated in the presence of chloramphenicol 

 have been studied both from the chemical and from the biological points 

 of view. It is known from the work of Hershey 159 and of Tomizawa, 160 that 

 the DNA formed after chloramphenicol action has all the characteristics 

 of a normal DNA; thus the chloramphenicol DNA synthesized in T 2 -in- 

 fected bacteria serves as a precursor for T 2 DNA, and behaves, therefore, 

 as a normal free DNA intermediate. 



The base composition of the chloramphenicol RNA is very similar to 

 that of normal RNA. 27 ■ 43 Thus the RNA formed in the absence of protein 

 formation seems to keep its chemical specificity. This is probably true also 

 for the biological specificity, at least for some RNA fractions such as the 

 sRNA. This sRNA is normally synthesized in the presence of chlorampheni- 

 col, since the ratio of sRNA to total RNA is kept constant as indicated by 

 chemical analysis 43 and by the fact that after doubling of the mass of RNA 

 in the presence of chloramphenicol, the RNA amino acid pool also dou- 

 bles. 161 It is not known, however, whether the pattern of the amino acids 

 attached to the sRNA is the same in the chloramphenicol sRNA as in the 

 normal sRNA. 



Though the chloramphenicol RNA bears some resemblance to the normal 

 RNA, it also exhibits some interesting differences. Neidhardt and Gros 110 

 observed that after bacteria have accumulated some RNA in the presence 

 of chloramphenicol, more than half of this nucleic acid is destroyed if the 

 bacteria are now transferred to a medium unable to support RNA synthesis 

 (buffer, or minimal medium in the case of an amino acid auxotroph). There 

 is very little destruction if the medium used for resuspending the treated 

 bacteria is able to support resynthesis of RNA. 



Since the chloramphenicol RNA can undergo degradation even in the ab- 

 sence of an energy source, it may be considered as the product of a passive 

 mechanism probably due to the effect of cellular ribonuclease. Consequently, 

 the amount of chloramphenicol RNA in the cell results from an equilibrium 

 between passive destruction and de novo resynthesis, and chloramphenicol 

 appears to shift the balance of the reactions towards net synthesis when 

 an energy source is available. 



159 A. D. Hershey and N. E. Melechen, Virology 3, 207 (1957). 



160 J. Tomizawa, Virology 6, 55 (1958). 



161 S. Lacks and F. Gros, unpublished results (1959). 



