The Biochemistry of the Bacterial Viruses 95 



preparation of the viral agents are very great, and critical estimates 

 of their degree of purity are difficult to make. 



A large part of our biochemical information about viral reproduction 

 is derived from a study of the T series of coliphages acting on 

 Escherichia coli. Though this has been partly a matter of necessity, 

 since the coliphages can be prepared easily and rapidly in sufficient 

 amounts for chemical work, it has also been hoped that the information 

 thus obtained could be applied, with suitable precautions, to other 

 members of the viral group. 



In what follows I have attempted to outline briefly the current status 

 of our biochemical knowledge of the coliphages. Rather than interrupt 

 such a description by continued documentation, I have omitted the 

 names of the individuals responsible for the facts recorded. It is to 

 be understood, of course, that our information is derived from the 

 efforts of a large number of investigators." 



Phages have been classified into two categories, virulent and tem- 

 perate, on the basis of their behavior towards suitable bacterial hosts. 

 These terms are equated with two types of relationships between virus 

 and host cell, the lytic and the lysogenic respectively. It will be 

 convenient to consider our information, both in regard to the types 

 of viruses and to the kinds of relationships, separately. 



Most of our knowledge concerning both chemical composition and 

 the biochemistry of the host-virus relationship is derived from the 

 virulent coliphages. Although there is some variation in the dimensions 

 given by various workers, there is general agreement that these parti- 

 cles are spermlike in shape, with hexagonal heads and tails of varying 

 length. They can be divided into four classes, each serologically un- 

 related to any other members of the group: the T, T 4 , and T, ; 

 coliphages. which are particles with fairly long tails (100-120x20 

 nut); T 3 and T 7 , which possess very short stubby tails; Ti, with a 

 long thin tail; and finally T 5 , also with a long thin tail. 



The virulent coliphages contain about equal amounts of protein and 

 nucleic acid of the DXA type. Complete analyses of the amino acid 

 content of the proteins of all the various coliphages have not yet been 

 made. However, in analogy with what has been observed in the 



* The reader interested in the original literature of the subject will find a very 

 complete background in S. E. Luria, General Virology, John Wiley A- Suns. 1953; 

 E. A. Evans. Jr., Bacterial Virus (with particular reference to synthesis of). .4;/;/. 

 R< v. Microbiol., S (1954); and C. A. Knight, The Chemical Constitution of 

 Viruses, in Advances in Virus Research, II. edited by K. M. Smith and M. A. 

 Lauffer, pp. 153-182. Academic Press, 1954. 



