106 BACTERIOPHAGES 



The phage-antibody system could be readily investigated by 

 the techniques of the quantitative precipitation reaction, but 

 the only attempt at such a study was made by Hershey, Kal- 

 manson, and Bronfenbrenner (1943a) using coliphage T2. 

 The authors concluded that the nitrogen of phage lysates which 

 was specifically precipitable by phage antibodies corresponded 

 to less than 10~^^ mg. N per lytic unit. Chemical analyses of 

 purified T2 phage preparations by various investigators agree 

 with a figure for the nitrogen content of the lytic unit which is 

 close to 10~i3 mg. (Chapter VII). The amount of antibody 

 nitrogen capable of precipitating with phage T2 was found to 

 be 0.6 mg. per ml. for a serum with a K value of about 360 min- 

 utes ~^ It would be of interest to know the ratio between anti- 

 body content and A' value for various other antiphage sera. 



With sera of low neutralizing antibody content, it is possible 

 to follow specific aggregation of phage by observing the con- 

 sequent reduction in plaque count (Lanni and Lanni, 1953; 

 Fodor and Adams, 1955). 



7. Agglutination of Phage-Coated Bacteria 



Individual cells of susceptible bacterial strains are able to 

 adsorb a considerable number of phage particles. Delbriick 

 (1940a) found that cells of E. coli became saturated after ad- 

 sorption of from 20 to 250 phage particles depending on the 

 physiological condition of the cells. Burnet (1933a) investi- 

 gated the serological properties of such phage-coated cells 

 using formalin-killed bacteria to avoid lysis. The formalinized 

 bacteria were suspended in a high-titer phage stock for an hour, 

 then centrifuged and washed to remove unadsorbed phage. 

 These phage-coated bacteria were less susceptible than uncoated 

 bacteria to agglutination by antibacterial sera, but were readily 

 agglutinated by antiphage serum which had no effect on un- 

 coated bacteria. The agglutination was phage-specific. Ab- 

 sorption of the serum with phage-coated bacteria depressed 

 both the agglutinating and the phage-neutralizing activities. 

 The result is interesting since it suggests that antigens capable 



