6o 



KOZLOFF ET AL. 



acid was investigated using doubly labeled host cells, 

 bacteria were labeled with N^^ and P^^ 



When the 



% of virus nucleic acid N from host 



=1.3 to 1.4 (Table IV), 



% of virus nucleic acid P from host 



While the results summarized in the discussions and conclusions in- 

 dicate that bacterial nucleic acids are the precursors of some of the 

 phage DNA, the ratio in the double labeling experiments is signifi- 

 cantly different from unity — the value expected for transfer of intact 

 host DNA to virus DNA (provided host and virus each has only one 

 and the same kind of DNA). This suggests utilization of nucleotides 

 or possibly of larger fragments of host nucleic acid for virus synthesis. 



Transfer of Purines and Pyrimidines from Host to Virus. — Radio- 

 active adenine has been isolated from E. coli grown on ammonium 

 lactate medium supplemented with NaHC^^Oa and has been used to 

 label the host. Bacteria were specifically labeled in the purine fraction 

 by culturing them on lactate medium supplemented with C^*-labeled 

 adenine. In this case both the adenine and the guanine of the cells are 

 equally labeled and account for all the radioactivity of the bacteria. 

 Phage was grown on the washed labeled cells, and the purines of the 

 phage were isolated. 



TABLE V 



TRANSFER OF LABELED PURINES FROM BACTERIAL HOST 

 TO BACTERIOPHAGE PROGENY 



* Quantities contained in 10" E. coli cells and resulting phage: 

 Bacterial DNA — adenine 1.08 mg., guanine 1.78 mg. 

 Phage DNA — adenine 3.68 mg., guanine 2.28 mg. 



In the first experiment (Table V) a large weight of carrier adenine 



