116 BACTERIOPHAGES 



dysentery host cells, whereas stronger bonds with E. coli would 

 still allow productive interaction. Both of these interpretations 

 attribute the observed effects to antibody-induced phenotypic 

 modification of host range, as opposed to selection from a genet- 

 ically ■ uniform, phenotypically heterogeneous population (see 

 Lanni and Lanni, 1956). Direct evidence that "monovalent" 

 survivors have indeed reacted with antibody in a significant 

 fashion is contained in a brief note by Lanni and Lanni (1957). 



12. Inheritance of Antigenic Specificity 



The perpetuation of serological character of phages during 

 continued subculture indicates, of course, that antigenic struc- 

 ture is genetically stable. On the other hand, the existence of 

 phage strains which show partial serological cross-reaction 

 implies the possibility of mutations affecting serological behavior. 



Efforts to demonstrate serological mutation in phage, by 

 examining either the survivors of prolonged serum action or 

 mutants selected for nonserological markers, have generally 

 been unconvincing (d'Herelle and Rakieten, 1934, 1935; 

 Burnet and Freeman, 1937) or unsuccessful (Luria, 1945a; 

 Hershey, 1946a, 1946b). Recent reports, however, indicate 

 that some success may have been achieved in isolating serolog- 

 ical mutants of a Xanthomonas pruni phage (Eisenstark, Goldberg, 

 and Bernstein, 1955) and of T5 (Lanni and Lanni, 1956, 1957). 

 Detailed verification of these briefly reported observations could 

 make the antigenic structure of these phages amenable to or- 

 dinary genetic analysis. 



Several workers, proceeding along a different line, have ob- 

 tained valuable information by examining hybrids obtained 

 from crosses of serologically related phages. Fodor and Adams 

 (1955) have shown that certain T5 X PB hybrids resemble one 

 or the other parent serologically, while others resemble both 

 parents to some extent. By contrast, Streisinger (1956b) 

 found that the genetic determinants of serological specificity 

 in T2 and T4 are allelic and inseparable from the host- 

 range determinants. Progeny from T2 X T4 crosses pos- 



