METABOLISM OF THE NUCLEIC ACIDS 419 



c. Bacitracin, Polymyxin, and Streptomycin 



These three substances are apparently without much effect on the syn- 

 thesis of nucleic acids by S. aureus although bacitracin in enormous con- 

 centrations (2 to 10 mg./ml.) does have a marked inhibitory action. ^^^-^^'^ 



VI. The Metabolism of Virus Nucleic Acids 

 1. The Origin of Virus Nucleic Acids 



It is well known that virus particles are rich in nucleic acid, and that in 

 an infected organism very considerable multiplication of virus particles 

 takes place. It is obvious therefore that a large amount of nucleic acid must 

 be synthesized in the course of this process. A useful account of several 

 aspects of virus multiplication is given in the report of a recent Symposium 

 of the Society for General Microbiology'^^ and in a review by Putnam. '^^ 

 A particularly good system for the study of the origin and fate of virus 

 nucleic acids has proved to be the Escherichia co/f-bacteriophage systems 

 which have been extensively employed to elucidate these reactions. 



Many aspects of the infection of E. coli with bacteriophage T2 have been 

 discussed by Heden/'*" and an excellent summary of the great volume of 

 isotope studies on bacterial viruses has recently been produced by Evans. '^' 



a. The Source of Bacteriophage Phosphorus 



Experiments have been carried out by Kozloff and Putnam'"*- '^^ and 

 Evans'^^ with the E. coli T^v^ system in which either E. coli cells labeled 

 with P^2 were incubated in an isotope-free medium with preprations of the 

 Te bacteriophage, or unlabeled bacterial cells were incubated in a P^^- 

 labeled medium with the phage particles. The virus particles produced in 

 these systems were then isolated and their isotope content measured. 



From experiments of this kind it was found that in synthetic medium 

 and in nutrient broth about 75 % of the virus DNA phosphorus was derived 

 from the phosphorus of the medium, while 17 to 31 % originated in the DNA 

 phosphorus of the host cells. These observations are in accord with those of 

 Cohen'^^ on the uptake of P^^ ^y bacteriophage T2 and T4 and mth the 



138 p Fildes and W. E. van Heyningen (eds.), 2nd Symposium Soc. Gen. Microbiol. 

 Cambridge (1953). 



139 F. W. Putnam, Advances in Protein Chem. 8, 175 (1953). 



1" C. G. Heden, Acta Pathol. Microbiol. Scand. Suppl. 88 (1951). 



"1 E. A. Evans, "Biochemical Studies of Bacterial Viruses." Univ. of Chicago Press, 



Chicago, 1952. 

 i« L. M. Kozloff and F. W. Putnam, J. Biol. Chem. 182, 229 (1950). 

 1" F. W. Putnam and L. M. Kozloff, Science 108, 386 (1948). 

 1" E. A. Evans, Bacteriol. Revs. 14, 210 (1950). 

 i« S. S. Cohen, /. Biol. Chem. 174, 295 (1948). 



c 



