160 BACTERIOPHAGES 



Step is temperature-dependent. The first step involves the for- 

 mation of salt linkages between charged groups on the phage and 

 host cell surfaces. Carboxyl and amino groups play the prin- 

 cipal role in a few systems which have been studied. In some 

 cases the phage receptor substance on the bacterial surface is a 

 major bacterial antigen. Bacterial extracts containing the 

 somatic antigen have the property of inactivating some phages. 

 Highly purified antigens in the form of complexes of lipid, pro- 

 tein, and polysaccharide retain this property. Treatment with 

 various chemical reagents has a diff'erential effect on the inhibi- 

 tory activity toward various phages. 



