516 BACTERIOPHAGES 



cles which must be adsorbed to the same bacterium to produce an 

 infective center must be increased. . . . 



Another interesting" observation made by Luria is that cross- 

 reactivation can occur within the group T2, T4, and T6. That 

 is, mixed infection of bacteria with inactivated T2 and inacti- 

 vated T6 will result in liberation of both T2 and T6 in an active 

 form. In order for reactivation to take place, both phages must 

 be capable of adsorption on the same host cell. For instance, in- 

 activated T2 is not reactivated by T6 when B/6 is the host cell. 



Methods of Studying Intracellular Growth of Bacteriophage 



The methods described so far have been devoted to study of 

 the properties of extracellular phage up to the moment of ad- 

 sorption to the host cell and after lysis of the host cell. Little 

 has been said about what happens inside an infected bacterium 

 during the latent period of intracellular phage growth. A 

 number of widely differing techniques have been applied to this 

 problem, some of the more novel of which will be described in 

 detail, and others briefly mentioned with references to the litera- 

 ture. 



Biochemical Methods 



Cohen and Anderson (1946) used the Warburg respirometer 

 to study the respiration of normal and phage- infected host cells. 

 The bacteria were grown in the chemically defined ammonium 

 lactate medium called F medium (p. 446). The Warburg ves- 

 sels contained 1.5 X 10^ bacteria in a total volume of 2 ml. of 

 F medium. To 1 was added 8 X 10^ active T2r+ particles, 

 to a second was added the same number of ultraviolet-in- 

 activated T2 particles, and the third vessel was a virus-free 

 control. The experiment was conducted at 38° C. Oxygen 

 uptake was measured continuously and the total CO2 evolution 



