METABOLISM OF THE NUCLEIC ACIDS 421 



the Te bacteriophage to the smaller T7 phage, using methods essentially 

 the same as those used with the larger virus. As with the Te phage, it was 

 found that there is considerable transfer of host nucleic acid nitrogen and 

 phosphorus to the viral progeny. The T7 phage differs from the Te in that 

 the latter synthesizes a high proportion of its DNA from products in the 

 medium, while the former, being smaller, has most of its requirement for 

 DNA met by the DNA of the infected cells, and there is little utilization 

 of components of the medium for DNA synthesis. 



2. The Fate of the Infecting Virus Particle 



Kozloff, in a recent review,^*^ and Putnam and Kozloff^** have examined 

 the fate of the phosphorus of the infecting Ter"*" phage particle by preparing 

 P^^-labeled samples of the virus and using them to infect unlabeled cells 

 in an isotope-free medium. It was shown that 50 to 60% of the isotope 

 appeared in the medium as low-molecular-weight compounds, and the 

 evidence suggests that the infecting particle is disintegrated on infecting 

 the bacterial cell. Of the remaining phosphorus, 10 to 15% was associated 

 with the bacterial debris (perhaps due to absorption of the newly formed 

 phage onto bacterial debris), while 20 to 40 % appeared in the viral progeny. 

 The liberation of acid-soluble phosphorus from infecting T2r+ phage has 

 been observed by Lesley et al.^^^'^^^ who have studied the liberation of P^^ 

 from labeled virus particles at different times after infection with different 

 proportions of virus per bacterial cell. 



These mechanisms have been further investigated by Kozloff'^^''®" 

 using Ter^ phage labeled with N'^ or with N'* and P^^ Again, there was 

 found to be a transfer of nitrogen from the parent phage to progeny amount- 

 ing to about 20% of the original isotope content of the infecting particle. 

 Sixty to 80 % of the remaining nitrogen was broken down to small molecules 

 and appeared in the medium. In another experiment labeled bacteria were 

 infected with phage and the phage progeny (labeled only in the DNA de- 

 rived from the bacteria) were isolated. These labeled phage were then used 

 to infect more unlabeled bacteria, when it was found that the proportion 

 of parent P^' appearing in the progeny was the same as in completely labeled 

 phage, indicating that the DNA of the phage which is derived from the 

 host, and that synthesized from the medium, participate to the same 



1" L. M. Kozloff, Exptl. Cell Research. Suppl. 2, 367 (1952). 



165 F w. Putnam and L. M. Kozloff, J. Biol. Chem. 182, 243 (1950). 



'*« S. M. Lesley, R. C. French, A. F. Graham, and C. E. van Rooyen, Can. J. Med. 



Sci.29, 128 (1951). 

 1" S. M. Lesley, R. C. French, and A. F. Graham. Arch. Biochem. 28, 149 (1950). 

 '5« R. C. French, A. F. Graham, S. M. Lesley, and C. E. van Rooyen, /. Bacteriol. 64, 



597 (1952). 

 '" L. M. Kozloff, /. Biol. Chem. 194, 83 (1952). 

 ISO L. M. Kozloff, J. Biol. Chem. 194, 95 (1952). 



