42 



VIRAL PROTEIN AND NUCLEIC ACID IN BACTERIOPHAGE GROWTH 



3. The ghosts are speciJ&cally adsorbed to phage-susceptible bacteria; the 

 DNA is not. 



4. The ghosts represent protein coats that surround the DNA of the intact 

 particles, react with antiserum, protect the DNA from DNase (desoxyribo- 

 nuclease), and carry the organ of attachment to bacteria. 



5. The effects noted are due to osmotic shock, because phage suspended in 

 salt and diluted slowly is not inactivated, and its DNA is not exposed to 

 DNase. 



TABLE II 



Sensitization of Phage DNA to DNase by Adsorption to Bacteria 



Phage adsorbed to bacteria for 5 minutes at 37°C. in adsorption medium, followed by 

 washing. 



Bacteria heated for 10 minutes at 80°C. in adsorption medium (before infection) or in 

 veronal buffer (after infection). 



Unadsorbed phage heated in veronal buffer, treated with DNase, and precipitated with 

 trichloroacetic acid. 



All samples fractionated by centrifuging 10 minutes at 1300 G. 



Sensitization of Phage DNA to DNase by Adsorption to Bacteria. — The struc- 

 ture of the resting phage particle described above suggests at once the possibil- 

 ity that multiplication of virus is preceded by the alteration or removal of the 

 protective coats of the particles. This change might be expected to show itself 

 as a sensitization of the phage DNA to DNase. The experiments described 

 in Table II show that this happens. The results may be summarized as fol- 

 lows: — 



1. Phage DNA becomes largely sensitive to DNase after adsorption to 

 heat-killed bacteria. 



2. The same is true of the DNA of phage adsorbed to live bacteria, and then 



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