38 



BACTERIOPHAGES 



most of the phage proteins and retained abihty to adsorb to and 

 kill bacteria. The phage nucleic acid presumably escapes 

 through cracks in the phage head and may be seen in electron 

 micrographs as long filaments about 20 A in thickness (Williams, 

 1953). These phage particles consist, therefore, of a nucleic acid 

 core surrounded by a membrane responsible for the overall 



Figure 2. Phage T2 seen inside bacteria infected 40 minutes earlier. UJ- 

 trathin sections prepared as described by Kellenberger, Ryter, and Schwab 

 (1956). X 32,400. Unpublished. 



shape of the particle (T. F. Anderson, Rappaport, and Musca- 

 tine, 1953). T5, as shown in a somewhat diff'erent manner, is 

 similarly constructed (Lark and Adams, 1953). 



Some additional features of the tail structure of phages T2 

 and T4 have been resolved in considerable detail. Kellenberger 

 and Arber (1955) observed stepwise changes in the morphology 



