THE SYNTHESIS OF BACTERIAL VIRUSES* 



II. THE ORIGIN OF THE PHOSPHORUS FOUND IN THE DESOXYRIBO- 

 NUCLEIC ACIDS OF THE T2 AND T4 BACTERIOPHAGES 



By SEYMOUR S. COHEN 



(From the Children's Hospital of Philadelphia (Department of Pediatrics) and the 



Department of Phijsiological Chemistry, School of Medicine, 



University of Pennsylvania, Philadelphia) 



(Received for publication, August 28, 1947) 



It has been shown that Escherichia coli B infected by T2 bacteriophage in 

 a synthetic medium, F, synthesizes protein-bound constituents containing 

 phosphorus and nitrogen at a constant rate (1). Evidence was presented 

 that suggests that the virus-infected cell synthesizes virus constituents 

 solely. This was most clearly indicated in the phosphorus metabolism, 

 since the only phosphorylated protein-bound constituent synthesized in the 

 infected cell was that characteristic of virus; i.e., desoxyribonucleic acid 

 (DNA). The ribonucleic acid (RNA) content of infected cells did not 

 increase. 



Although the data presented suggested that the materials formed during 

 infection were derived from the medium as in normal cells, it had not been 

 proved that the nucleic acid phosphorus found in virus was not derived from 

 cellular substance existing prior to infection, or had not been in normal host 

 constituents during infection prior to appearance in virus. It seemed un- 

 likely that the virus nucleic acid was derived from the host DNA, since sev- 

 eral times more DNA was synthesized after infection than was originally 

 present. However, it was possible that the RNA of the infected cell pos- 

 sessed an active turnover yielding its phosphorus to DNA nucleotides, while 

 the RNA was continually replaced with nucleotides whose phosphorus was 

 derived from the medium. 



Two basic problems were therefore posed. (1) Was the DNA-P of virus 

 derived from the phosphorus in the host prior to infection? (2) Was RNA 

 a precursor of DNA? These hypotheses were tested by means of radio- 

 active phosphorus, P^'. 



EXPERIMENTAL 



Conditions for Optimal Virus Yield — A single generation of virus multipli- 

 cation was studied under conditions of multiple infection. The possibility 

 was therefore eliminated that the generations of virus produced after the 

 first generation in a medium of known composition would be affected by the 



*Thp work described in this paper was aided by the Office of Naval Research. 



Reprinted by permission of the author and the American Society 



of Biological Chemists, Inc. from The Journal of Biological 



Chemistry, 174 (1), 295-303 (1948). 



116 



