FATE OF INFECTING PHAGE PARTICLES 



221 



phage as a carrier, the lysate was fractionated in the usual way 

 and only 1 .6 per cent of the parental P^^ was found in (he phage 

 fraction. In a second sample lysed at 34 minutes, the burst size 



high speed pellet 



ow speed pellet 



ocid-soluble 



10 20 30 40 50 60 70 80 90 



MINUTES AFTER INFECTION 



Figure 8. Transfer of radiophosphorus from parental to offspring phage T2. 

 The curves show distributions of P^^ measured by centrifugal fractionation of 

 lysates prepared at different times after infection with 3 labeled phage particles 

 per bacterium. The vertical lines span the observed range of variation in 

 three independent experiments. Acid-soluble P^^ is measured from separate 

 aliquots of unlysed culture. P^^ not accounted for is DNA nonsedimentable 

 after lysis. The dashed line shows infective phage particles per bacterium 

 released during lysis. These are distributed, independently of time of lysis, 

 in the ratio 14 : 86 between low and high speed pellets, and account for the 

 rise in both fractions after 10 minutes. The observed efficiency of transfer 

 is therefore about 60/0.86 = 70%. The rise in acid-soluble P^- is probably 

 the combined result of superinfection breakdown of readsorbed offspring 

 particles and enzymatic destruction of phage-precursor DNA, both occurring 

 after lysis of some bacteria at about 25 minutes. Experiments by A. D. Her- 

 shey, unpublished. 



