442 F. GROS 



/3-galactosidase, constitutively or adaptively, declines at the same rate as 

 does the ability to produce colonies. This suggests that the DNA (or the 

 nucleus) functions as a unit in the synthesis of specific enzymes, since, for 

 one particular enzyme, destruction of any part of the DNA structure (and 

 not only the relative destruction of the gene) suppresses the synthesis of 

 this enzyme. 



While a few phosphorus disintegrations in the DNA may drastically re- 

 duce the capacity of a bacterium to synthesize a specific enzyme, they do 

 not reduce the formation of protein or RNA at a comparable rate. These 

 results give the general impression that DNA could exert an indirect con- 

 trol on the capacity to form RNA and polypeptides, while controlling di- 

 rectly the organization of polypeptides into specific proteins. 



If this is so, it would be expected that injection of intact DNA molecules 

 into a bacterium which had lost its ability to form enzymes, as the re- 

 sult of P 32 decay, would restore this ability immediately. Such an experi- 

 ment has not been performed as yet with bacterial DNA (by transforma- 

 tion or recombination) but it has been observed that after infection of such 

 "P 32 inactivated" bacteria by a bacteriophage, the infected bacteria syn- 

 thesize phage protein, that is protein specific for the newly injected DNA 

 in the usual way. 178 



This experiment has to be considered in the light of our knowledge that 

 in bacteria infected by T 2 phage, the chromosomes are destroyed and the 

 host becomes unable to synthesize protein specific for the missing DNA, 179 

 although it now produces protein structurally related to the infecting DNA. 

 On the other hand, when the integrity of the DNA is preserved, as after 

 an infection by a temperate phage, synthesis of bacterial enzymes can 

 still be performed. 180 



Interestingly, the fact that DNA integrity is required for enzyme syn- 

 thesis in E. coli is in conflict with the data obtained from enucleation experi- 

 ments in higher organisms. 173, 176 The mechanism for transferring the genetic 

 information to the protein-forming site, although it may be the same in 

 bacteria as in more complex cells, would appear to function in a discontin- 

 uous manner in the latter case, and in a continuous manner in the former 

 case. 



2. RNA Content and Rate of Protein Synthesis 



The problem of the part played by RNA as an intermediate between 

 DNA and the protein-forming machinery has been studied by two distinct 

 methods. The first method is to establish whether there exists a direct rela- 



178 G. S. Stent and C. R. Fuerst, Advances in Biol, and Med. Phys. 7, in press. 



179 J. Monod and E. Wollman Ann. inst. Pasteur 73. 937 (1947). 



180 L. Siminovitch, Ann. inst. Pasteur 84, 265 (1953). 



