S. S. COHEN 



297 



this high speed centrifugation, containing more than 5 per cent of the 

 activity of the lysate, were analyzed for protein-bound P and DNA. Virus 

 was isolated from the high speed sediments as described previously (3, 4). 

 The distribution of these substances in the four lysates is given in Table I. 

 It may be seen that the largest amounts of DNA and P appear in the 

 virus-containing fraction; i.e., the high speed sediment. When this fraction 

 was resuspended in 5 cc. of 0.85 per cent NaCl and centrifuged at 4000 

 R.p.M. for 30 minutes, approximately 25 per cent of the DNA of the fraction 

 had become insoluble. After dialysis of this supernatant fluid against 

 running water overnight, the once sedimented virus concentrate had 

 DNA-P to total P ratios which were very close to 1.0. These values for 

 isolated dialyzed virus after one differential centrifugation cycle were 



Table I 

 Distribution of Protein-Bound P and DNA in Lysates of Infected Bacteria 



T4A 1.05, T4B 1.00, T2D 1.02. Thus the conditions described above yielded 

 fractions with the characteristics of virus whose inorganic P contents were 

 so low as to be undetectable. 



Infected cells may synthesize as much as 7 to 8 times as much DNA as 

 was originally present. In many cases, at least 3 times as much DNA was 

 isolated in the virus as was present in the bacteria at the onset of infection. 

 It is considered probable that DNA formed after infection and not recov- 

 ered in isolated virus was nevertheless originally part of the virus and was 

 lost either by adsorption to debris or by becoming insoluble as a result of 

 high speed centrifugation. No indication has been obtained in prepara- 

 tions of either T2r+ or T4r"^ bacteriophage from F lysates that a phosphoryl- 

 ated compound other than DNA is present in either virus. Furthermore, 

 in contrast to the observations of Taylor (5), preparations of these viruses 

 from nutrient broth lysates prepared from infected cells as described above 

 also possessed DNA-P to total P ratios of 1.0 (6). Hence no evidence has 



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