476 BACTERIOPHAGES 



TABLE XXIII 



Plaque Counts on Plates from First and Second Growth Tubes 



Time, min. F.G.T. S.G.T. 



15 98 



17 105 



19 93 



20 



21 110 



22 72 



23 520 



24 38 



25 About 4000 



26 52 

 28 78 

 30 92 

 32 110 

 34 123 

 36 114 

 40 98 

 50 107 

 60 115 



against the time after initiation of adsorption. The latent 

 period, rise period and final stationary period are clearh- evi- 

 dent, as is burst size. 



Discussion 

 This experiment was designed for a one-step growth curve 

 under conditons of single infection; i.e., the proportion of 

 bacteria infected with 2 or more phage particles is small. 

 The input ratio of phage to bacteria was 0.1, and with 80 per 

 cent adsorption the multiplicity of infection was 0.08. Since 

 the distribution of phage particles among the bacterial popu- 

 lation follows the Poisson formula (p. 470), the proportion of 

 bacteria not infected at all is 0.923, the proportion infected 

 with 1 phage particle is 0.074, and the proportion infected with 

 2 or more phage particles is the remainder, or 0.003. Hence 

 the proportion of infected bacteria that are multiply infected is 

 0.003/0.074 = 4 per cent. To increase the proportion of multiply 

 infected bacteria, one simply increases the multiplicity of in- 



