ADSORPTION OF PHAGE TO HOST CELL 157 



affecting the antigenicity of the mucoprotein, but the polysac- 

 charide and protein separately are nonantigenic. 



The most intensive study of the phage-inhibiting activity of 

 purified bacterial antigens was made by Goebel and collabora- 

 tors using Sh. sonnei and the T series of coli-dysentery phages. 

 Phase I of Sh. sonnei is susceptible to phages T2 and T6 but resist- 

 ant to the other T phages. Phase I organisms mutate to phase 

 II, which is serologically distinct from phase I, and concomi- 

 tantly become susceptible to phages T3, T4, and T7 in addition 

 to T2 and T6. The somatic antigens of phase I and phase II 

 cultures have been shown to be lipocarbohydrate-protein com- 

 plexes (Baker, Goebel, and Perlman, 1949). The highly puri- 

 fied and electrophoretically homogeneous antigens were tested 

 for phage-inhibiting activity by Miller and Goebel (1949). 

 Phages T2 and T6 were inhibited by neither antigen, and phages 

 T3, T4, and T7 were inhibited by the phase II antigen only. 

 The diluent used had a marked effect on the extent of inhibition. 

 T3 and T7 were strongly inhibited in broth but not in buffer. 

 A tryptophan-requiring strain of T4 was inhibited in broth but 

 not in buffer unless tryptophan was added. A variant of T4 

 which did not require tryptophan was inhibited equally well in 

 buffer and broth. These results again suggest that the role of 

 tryptophan is in the attachment of phage T4 to the bacterial re- 

 ceptor substance. They also suggest the possibility of a cofactor 

 requirement for T3 and T7. 



Heat treatment of the phase II antigen resulted in rapid loss 

 of phage-inhibitory activity. Digestion with pancreatin followed 

 by dialysis and deproteinization by shaking with CHCI3 and octyl 

 alcohol yielded a lipocarbohydrate with negative tests for pro- 

 tein. This material was fully active serologically and essentially 

 as active as the undegraded somatic antigen in its ability to in- 

 hibit plaque formation with phage T4. The material is similar 

 to that isolated by Gough and Burnet (1934) from autolyzed cul- 

 tures oiSh.flexneri. 



By using somewhat different isolation procedures, Jesaitis and 

 Goebel (1952) isolated a phase II antigen which inactivated 



