208 ROBERT L. SINSHEIMER 



development of T2 serum blocking power in infected cells 105 ' 106 indicate 

 that the synthesis of the tail antigen of T2 begins at about 9 to 10 minutes 

 after injection — a few minutes after the initiation of phage DNA synthesis, 

 and 2 to 3 minutes before the first appearance of mature phage particles. 



Studies of protein synthesis by S 35 -labeling indicate that virtually no S 35 

 assimilated before infection enters into phage particles. 104 During the first 

 10 minutes of the infection, protein synthesis continues at a rate comparable 

 to that in uninfected cells" 3 ' 100 ' 106a but little of this is precursor to phage 

 protein. By 10 minutes some 3 to 4 units of phage protein (one unit of 

 phage protein = 2 X 10~ 12 ng. S 100 ) have been made, representing about 8 % 

 of the total protein synthesis in these 10 minutes. 



Once initiated, a pool of some 15 units of phage precursor protein is 

 accumulated and maintained at a nearly constant level, while it is drawn 

 upon for the production of complete phage particles. During this period of 

 constant pool size, about 60 % of all protein synthesis in the infected cell is 

 used to maintain the pool. 100 



Once initiated, the production of mature phage particles continues at 

 a rate only slightly less than the rate of synthesis of phage DNA so that 

 the pool of phage DNA continues to grow but at a very much slower rate 

 (in synthetic medium the rate of phage maturation is about 4.4 particles/ 

 cell/minute compared to a rate of DNA synthesis of 5 units/cell/minute 100 ). 



(2) Effect of Inhibition of Protein Synthesis upon the Development of Phage 

 DNA. Chloramphenicol at concentrations of 10 ng. per milliliter or greater 

 almost completely blocks protein synthesis in E. coli, but permits DNA and 

 RNA synthesis to continue at a constant (linear) rate for at least 40 min- 

 utes at 37°. 107 



When chloramphenicol is added to T2 infected cultures of E. coli after 

 the eclipse period, phage synthesis is stopped after about a 2-minute lag. 

 If chloramphenicol is added during the eclipse period, phage protein is 

 never produced unless the chloramphenicol is later removed. The effect of 

 chloramphenicol upon the development of phage DNA is dependent upon 

 the time, after infection, of the initial exposure to chloramphenicol. If 

 chloramphenicol is added before infection, at infection, or during the first 

 4 minutes after infection, there is no subsequent synthesis of phage DNA. 

 If chloramphenicol is added between the fifth and twelfth minute, during 

 the period of normally increasing rate of DNA synthesis, DNA production 

 continues in the presence of chloramphenicol but at just the rate which 



105 R. I. De Mars, Virology 1, 83 (1955). 



106 A. D. Hershey, G. Koch, A. W. Kozinski, J. D. Mandell, R. Thomas, and J. 

 Tomizawa, Carnegie Inst. Washington Yearbook 57, 379 (1958). 



106a I. Watanabe, Biochim. et Biophys. Acta 25, 665 (1957). 



107 J. Tomizawa and S. Sunakawa, /. Gen. Physiol. 39, 553 (1956). 



