33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 189 



mary of current ideas concerning the biochemical and biophysical aspects 

 of this process as exemplified in the T-even phages. 11 The evidence from 

 which these ideas have been developed will then be presented in detail. 

 The time scale, for the events to be described, pertains to experiments per- 

 formed at 37°. 



All the bacterial viruses thus far investigated have been found to contain 

 deoxyribonucleic acid (DXA) to the extent of 25-50% by weight. 4 Most 

 of the remainder of the viral mass is protein. 14 In the T-even bacteriophages 

 several proteins are known to be present, including a "head" protein, 15 " 17 

 enclosing most of the nucleic acid, "tail" proteins which serve as a mech- 

 anism of adsorption to and penetration of the host, 15 ' 18 " 22 and certain 

 "internal" proteins of uncertain function. 23 " 25 In addition, certain dibasic 

 amines 26 have been found which serve as a portion of the neutralizing 

 charge to the nucleic acid. 



In an appropriate medium, a T-even phage particle adsorbs to the sur- 

 face of a susceptible bacterium by means of an adsorption site located on 

 its tail. Following adsorption, an enzymic process of penetration 27, 27a - 28 



11 The process of bacteriophage infection has been studied largely with a group of 

 seven phages which attack a common host, strain B of Escherichia coli. These 

 seven 12 known as the T phages, were independent isolates but were later shown 

 to fall into related classes. One of these classes, which by accident includes T2, 

 T4, and T6 (the "T-even phages"), has been shown to have several uniquely favor- 

 able characteristics, and hence has been the object of the great bulk of bacterio- 

 phage research. The results of the investigation of the nucleic acids of this sub- 

 group will be considered first (Phage C16 has been shown to be closely related to 

 the T-even phages 13 and may be included with this group). 



12 M. Demerec and U. Fano, Genetics 30, 119 (1945). 



13 M. H. Adams, /. Bacteriol. 64, 387 (1952). 



14 About 1% of the phosphorus of a T2 phage is acid-soluble (Kozloff 21 ). A portion 

 of this is known to be present as ATP and dATP which are involved in contraction 

 of the phage tail during injection. 



15 R. C. Williams and D. Fraser, Virology 2, 2S9 (1956). 



16 H. Van Vunakis and J. L. Barlow, Federation Proc. 15, 620 (1956). 



17 H. Van Vunakis, W. H. Baker, and R. K. Brown, Virology 5, 327 (1958). 



18 E. Kellenberger and W. Arber, Z. Naturforsch. 10b, 698 (1955). 



19 L. M. Kozloff, M. Lute, and K. Henderson, /. Biol. Chew. 228, 511 (1057). 



20 E. Kellenberger and J. Sdchaud, Virology 3, 256 (1957). 



21 L. M. Kozloff and M. Lute, J. Biol. Chem. 234, 539 (1959). 



22 S. Brenner, G. Streisinger, R. Home, S. P. Champe, L. Barnett, S. Benzer, and 

 M. W. Rees, J. Mol. Biol., 1, 281 (1959). 



23 A. D. Hershey, Virology 1, 108 (1955). 



24 A. D. Hershey, Virology 4, 237 (1957). 



26 L. Levine, J. L. Barlow, and H. Van Vunakis, Virology 6, 702 (1958). 



26 B. X. Ames, D. T. Dubin, and S. M. Rosenthal, Science 127, 814 (1958). 



27 D. D. Brown and L. M. Kozloff, J. Biol. Chem. 225, 1 (1957). 

 27a G. Koch and W. J. Dreyer, Virology 6, 291 (1958). 



28 P. P. Dukes and L. M. Kozloff, J. Biol. Chem. 234, 534 (1959). 



