The Biochemistry of the Bacterial Viruses 97 



There has been much discussion of the living or non-living nature 

 of the viruses, and there is no need bo labor the matter further here. 

 However, such viral particles as the bacteriophages and the tobacco 

 mosaic viruses do not show demonstrable metabolic activity, do not 

 contain energy "reservoirs," nor require any source of energy to main- 

 tain their structure. It appears, therefore, that we are dealing with 

 structures which, although enormous in terms of molecular size, are 

 bound together by the usual covalent bonds, together with such other 

 types of intramolecular binding forces as operate, for example, in 

 determining the particular configuration of a protein molecule. An 

 attempt to elucidate the chemical details of such structures is formi- 

 dable enough but one which can be faced by the chemist with more 

 equanimity, certainly, than the effort to describe in molecular terms 

 such metabolizing systems as a single bacterial cell or an erythrocyte. 



The adsorption of virulent viral particles by a sensitive host is 

 followed by a sequence of reactions of which the chemistry is under- 

 stood only in part. With T 2 , T 4 , and T 6 , the tail constitutes the point 

 of attachment to the sensitive bacterial host. In its initial phase, the 

 adsorption process is reversible and depends on the existence of com- 

 plementary electrostatic and geometric relationships between the virus 

 and certain portions of the host cell wall. In To, the positively charged 

 amino groups of the virus particle bind the negative carboxyl radicals 

 of the bacterial cell wall, whereas in Ti, both types of groups on both 

 surfaces participate in the reaction. The initial reversible binding of 

 the phage is followed by an irreversible phase, which probably involves 

 changes in both the virus particle and the bacterial cell wall. 



The difficulty of isolating the earlier phases of the infectious process 

 in the in vivo system has led to a study of the interaction between the 

 coliphages and so-called "bacterial membranes." These are prepared 

 by autolysis of heavy suspensions of E. coli in buffer solutions and 

 subsequent treatment with proteolytic enzymes and with lysozyme. 

 Such preparations are homogeneous and specifically adsorb and in- 

 activate coliphages which attack the original bacterial cell. If one 

 follows the interaction between phage and membrane by means of the 

 electron microscope, actual dissolution of the membrane can be shown. 

 The process can also be studied chemically by using bacterial mem- 

 branes in which the nitrogen has been marked by using N 15 . When 

 such membranes are treated with coliphage, quantities of soluble ni- 

 trogenous compounds are released proportional to the quantity of phage 

 added. The chemical nature of these compounds is presently being 



