302 BACTERIAL VIRUSES. II 



P of the medium. It is not known in what compounds the radioactivity 

 resided. 



DISCUSSION 



It may be seen from the data presented in this paper that the hypotheses 

 suggested in Paper I have been verified by means of the isotope technique. 

 These are (1) that phosphorylated virus constituents are synthesized in the 

 main from P assimilated from the medium after infection, and (2) that RNA 

 after infection has a very low, if any, turnover rate, and is not a precursor 

 of virus DNA. 



Nevertheless the radioactivity of the virus P was significantly different 

 from that of the P of the medium. It has been observed that a very small 

 amount of virus multiplication may occur in the absence of external P (11). 

 Therefore it appears that some of the P of the host may be incorporated into 

 virus. It is considered likely that this small amount of P is derived from 

 the intracellular pool of inorganic P or low molecular weight organic P 

 which can equilibrate with P assimilated after infection. This intracellular 

 metabolic pool would be used for the synthesis of DNA after infection and 

 possibly even before the P assimilated after infection. Thus in short term 

 experiments involving r strains the percentage of host P appearing in virus 

 may conceivably be greater than that observed in these long term experi- 

 ments with r+ type virus. This remains to be tested. 



Many workers have found that protein and DNA syntheses are accom- 

 panied by a vigorous RNA metabolism in a wide variety of tissues. In 

 addition it has been reported that there is apparently a conversion of ribose 

 nucleotides to desoxyribonucleotides in the early stages of cleavage of the 

 fertilized sea-urchin egg (12). These data are ably reviewed by Brachet 

 (13). In the system described in these papers, none of these phenomena are 

 to be observed. It appears possible to study the precursors of DNA in this 

 system uncomplicated by the metabolism of RNA. 



I am indebted to Dr. Samuel Gurin of this University and Dr. M. Kamen 

 of Washington University for their advice and assistance in the course of 

 these studies. I wish to thank Miss Catherine Fowler for her technical 

 assistance. 



SUMMARY 



The preparation and properties of bacterial lysates after multiple infec- 

 tion have been described. As a result certain isotope experiments requiring 

 viral isolation could be performed. The distribution of the bacterial and 

 viral components in these lysates has been studied. It has been found pos- 

 sible to recover in a purified concentrate of virus much of the P assimilated 



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