1 86 BACTERIOPHAGES 



Figure 7 shows an electron micrograph of the products re- 

 leased by lysis of bacteria infected with T2 in the presence of pro- 

 flavine. 



The same and other intermediate structures related to viral 

 growth have been detected by serological methods (Chapter 

 VIII) and by chemical methods (Chapter XIV). The total in- 

 formation may be summarized as follows. Infected cells con- 

 tain at least four phage-specific materials in addition to phage 

 particles: free DNA, doughnuts, tail pins, and free tail antigen, 

 all separable from each other in lysates. Only free tail antigen 

 and free DNA are caused to accumulate by proflavine, that is, 

 proflavine does not aff'ect the total amount of these substances 

 formed, but suppresses their incorporation into phage particles 

 (DeMars, 1955; Kellenberger and Sechaud, 1957). 



Doughnuts, tail antigen, and tail pins are probably made of 

 protein. Tail antigen might be expected to correspond to the 

 tail fibers of phage particles. When prepared by degradation of 

 phage particles, the fibers can adsorb to bacteria (Williams and 

 Fraser, 1956). Free tail antigen found in premature lysates, 

 however, cannot. The significance of this difference cannot 

 now be assessed, because present information about the adsorp- 

 tion characteristics of materials found in premature lysates seems 

 to be unreliable. Thus doughnuts never adsorb, but Maal0e and 

 Symonds (1953) reported adsorption of an S^Mabeled fraction in 

 T4 lysates that should have been chiefly doughnuts. Kellen- 

 berger and Sechaud (1957) observed adsorption of tail pins 

 found in T2 lysates, but none of the materials, including phage 

 particles, found in their T4 lysates would adsorb. Unfortu- 

 nately little of the work with premature lysates has been carried 

 out with adequate precautions to prevent interactions between 

 phage-specific materials and bacterial debris in the lysates, 

 partly because these interactions are not themselves understood 

 (Sagik, 1954) (Chapter XVI). 



The free DNA found in premature lysates undoubtedly is a 

 phage precursor (Hershey, 1953a). Some of the antigenic pro- 

 tein is, too (Maal0e and Symonds, 1953; Hershey, 1956b). 



