CONTENTS XV 11 



Concentration and purification of phage 457 



Preparation and use of antiphage sera 461 



Immunization cf animals 461 



Assay of antiphage sera 463 



Use of K value of antiserum to demonstrate 



serologic relatedness among phages 465 



Rate of adsorption of virus to bacterium 466 



1 . Assay of unadsorbed phage 467 



2. Determination of number of infected bac- 

 teria 469 



3. Determination of proportion of surviving 

 bacteria ^'^^ 



The single-step growth curve 473 



Discussion ^'^ 



Lysis 481 



Adsorption of phage without phage develop- 

 ment ••• 483 



Investigations of chemical action on virus 



growth 4o4 



Single-cell method of studying virus multiplication ... 485 



Host cell mutation to resistance to virus attack 490 



Isolation of phage-resistant mutants 490 



Mutational pattern of strain B of £". coli 492 



Indicator strains and their properties 494 



Plating of mixed viruses with mixed indicator 



495 



strains ^^-' 



Mutations of bacteriophages 501 



1. Host range mutations 501 



2. Adsorption cofactor mutations 503 



3. Plaque morphology mutations 505 



Mixed infection and genetic recombination 508 



Mixed infections with r+ and r variants of 



same phage type 508 



Recombination of genetic characters in mix- 



edly infected bacteria 509 



Effects of ultraviolet irradiation of bacteriophage 511 



Photoreactivation 513 



Multiplicity reaction of ultraviolet-inactivated 



phages 514 



