188 ROBERT L. SINSHEIMER 



the new virus particles, of the genetics of the virus particle, and of the 

 interaction of viral genomes with each other and with the host genome. 3-9 



Several circumstances have combined to favor rapid progress in the bac- 

 terial virus field. The assay method is rapid and precise. 9 ' 10 The ability 

 to grow the host cells on chemically defined media has greatly facilitated 

 the production of virus particles with varied kinds of radioactive, chemical, 

 or density labels. It has been readily possible to obtain purified virus 

 preparations in which a large fraction of the particles could be demon- 

 strated to be infective, thereby insuring that the chemical and physical 

 properties of the bulk virus preparations represented the properties of the 

 infectious entity. 



It has been easily possible to obtain essentially simultaneous infection 

 of an entire bacterial culture, thereby permitting the detailed study of the 

 nature and sequence of events in viral infection. At least for the larger 

 bacteriophages, the ratio of the mass of the infecting particle to the mass 

 of the host cell has been several orders of magnitude greater than is the case 

 for the other classes of viruses, so that even the early stages of infection 

 produce significant quantitative and readily observable effects upon the 

 metabolic processes of the host. In addition, one must mention the great 

 ingenuity displayed by a considerable group of investigators in devising 

 means to exploit these intrinsic advantages. 



This chapter will attempt to review the information presently available 

 concerning the structures of the nucleic acids of the bacterial viruses, the 

 functions of these nucleic acids in viral infection, and the manner of repli- 

 cation of these nucleic acids. The information to be considered will be pri- 

 marily that derived from biochemical or biophysical experiments. Evidence 

 from radiobiological or genetic experiments will be used to supplement 

 direct biochemical or biophysical evidence and, when appropriate, to sup- 

 port particular interpretations. 



2. Some General Features of Bacteriophage Infection 



a. The Process of Infection with T-Even Phages 



Bacteriophage replication is a complex process of biosynthesis and mo- 

 lecular organization. For clarity it will be desirable to present a brief sum- 



3 M. Delbruck, Biol. Revs. Cambridge Phil. Soc. 21, 30 (1946). 

 J F. W. Putnam, Advances in Protein Chem. 8, 177 (1953). 



5 A. D. Hershey, Advances in Virus Research 4, 25 (1957). 



6 G. S. Stent, Advances in Virus Research 5, 95 (1958). 



7 G. Bertani, Advances in Virus Research 5, 151 (1958). 



8 S. Brenner, Advances in Virus Research 6, 137 (1959). 

 8a G. S. Stent, Advances in Biol. Med. Phys. 7, in press. 



9 M. H. Adams, "Bacteriophages." Interscience, New York, 1959. 



10 M. H. Adams, in "Methods in Medical Research" (J. H. Comroe, ed.), Vol. 2, p. 

 1. Year Book Publishers, Chicago, 1950. 



