420 R. M. S. SMELLIE 



more general studies of Cohen ''*^'" on the synthesis of nucleic acids by 

 bacteriophate T2 , T4 , and Te . 



b. Bacteriophage Nucleic Acids Studied with A^'* and C^* 



Kozloff et a^.'"^ and Siddiqi et a/.,"^ in studies on the E. coli Te bacterio- 

 phage system with the aid of N'^-labeled host cells and medium, have made 

 observations closely confirming those made with P^'-. Thus when the Ter^ 

 phage was grow^n on unlabeled bacteria in an N' ^-labeled medium, about 

 66% of the virus DNA formed w^as found to be derived from the medium, 

 while in the complementary experiment in which the bacteria were labeled, 

 from 16 to 40% of the virus nucleic acid nitrogen originated in the nitrogen 

 of the infected cells. Similar amounts of bacterial nitrogen were found in 

 each of the bases derived from the virus nucleic acid. The extent of transfer 

 of bacterial nitrogen to virus nitrogen was decreased when the nitrogen 

 content of the medium was raised by the addition of ammonium chloride 

 or purine bases, but, even in the presence of a large excess of medium nitro- 

 gen, considerable transfer of bacterial nitrogen to the viral progeny oc- 

 curred. 



In experiments in which the bacteria were labeled with N^^ and P^^, it 

 was noted that there was a relatively greater transfer of bacterial nitrogen 

 than of bacterial phosphorus to the virus DNA, suggesting that, while the 

 transfer may involve the bases of the bacterial DNA, it is probably not 

 purely a transfer of nucleotides or polynucleotides. 



Koch et al.^^^ have investigated the transfer of host purines to the phage 

 progeny using bacteria in w^hich the purines alone were labeled with C^^. 

 It was found that from 14 to 24 % of the phage adenine and 20 to 35 % of 

 the phage guanine was derived from the bacterial purines and that only 

 the purines of the phage were significantly labeled. In other experiments 

 w here the bacterial purines w^ere labeled with C" and the remaining nitrogen 

 of the bacteria with N'*, it was apparent that only the purines of the bac- 

 teria were converted to phage purines. Similar utilization of host pyrimi- 

 dines in the formation of phage pyrimidines has been noted by Weed and 

 Cohen.15' 



Recently Putnam and his co-workers'^'- '^^^ have extended their studies of 



'" S. S. Cohen, J. Biol. Chem. 174, 281 (1948). 



'*'' S. S. Cohen, Bacteriol. Revs. 15, 131 (1951). 



i« L. M. Kozloff, K. Knowlton, F. W. Putnam, and E. A. Evans, J. Biol. Chem. 188, 



101 (1951). 

 "9 M. S. H. Siddiqi, L. M. Kozloff, F. W. Putnam, and E. A. Evans, /. Biol. Chem. 



199, 165 (1952). 

 15" A. L. Koch, F. W. Putnam, and E. A. Evans, J. Biol. Chem. 197, 113 (1952). 

 1^' L. L. Weed and S. S. Cohen. /. Biol. Chem. 192, 693 (1951). 



'« F. W. Putnam, D. Miller, L. Palm, and E. A. Evans, J. Biol. Chem. 199, 177 (1952). 

 153 F w. Putnam, Exptl. Cell Research. Suppl. 2, 345 (1952). 



