410 BACTERIOPHAGES 



TABLE XX 



Serological Groups of the Type-Determining Temperate Phages of Salmonella 



typhi 



Group 1 Group 2 Group 3 Group 4 



b3 (a) dl (d6 t 



28' (b) k (a) -!f2 



(30' 



Phages d6, f2, and 30' are serologically indistinguishable from 

 each other. Phages 25' and 26' however, which form a sepa- 

 rate subgroup, do not show appreciable relationship to the 

 remainder of group 3, nor is their relationship to each other as 

 close as that of the other members of the group. 



In view of the constant connection between the specificities 

 of lysogenic Vi-types of S. typhi and the prophages they carry, 

 it was suggested by Luria (1953b) that lysogenically determined 

 types be designated by the symbol of the nonlysogenic precursor 

 type followed by that of the determining phage in parentheses. 

 This provides a sort of structural formula for the types concerned 

 and the suggestion was adopted and developed by Anderson 

 (1955a, 1956) and Anderson and Fraser (1955). A few exam- 

 ples of this method of symbolization are shown in Table XXI. 



TABLE XXI 



Structural Formulae of Vi-Types oi Salmonella typhi 



