444 



INACTIVATION OP BACTERIOPHAGES 



merited and washed three times in nutrient broth by high speed centrifugations (60 

 minutes at 10,000 r.p.m. for T2, T5; 90 minutes at 15,500 r.p.m. for Tl, T3, T7). 

 The number of plaque-forming units and the P^' content of the purified suspension 



8 



8 12 DAYS 



1 1 1 



A 0=270 ma/mg. 



1. 



^. 



1 1 1 



Ao=220mc./mg. 





\o 



A - 



\ 



T2 



I I 



02 0.4 0.2 0.4 j-e"^^ 



Fig. 1. P32 inactivation of Tl, T2, T3, T5, T7, and X at +4°C. Ao = specific ac- 

 tivity of growth medium. 



were then assayed and the phosphorus content per infective unit calculated on the 

 basis of the specific activity of the growth medium. In each case, more than 90 per 

 cent of the P^^ of the purified suspension could be adsorbed specifically to sensitive 

 bacterial cells, indicating that practically all the radioactivity resided in morpho- 

 logically intact bacteriophage particles. The results of this analysis agree well with 

 the phosphorus content of T2 determined by Hershey, Kamen, Kennedy, and Gest 



283 



