A. D. HERSHEY AND MARTHA CHASE 



41 



the phage. The radiochemical purity of the preparations is somewhat uncertain, ow- 

 ing to the possible presence of inactive phage particles and empty phage membranes. 

 The presence in our preparations of sulfur (about 20 per cent) that is precipitated by 

 antiphage serum (Table I) and either adsorbed by bacteria resistant to phage, or 

 not adsorbed by bacteria sensitive to phage (Table VII), indicates contamination 

 by membrane material. Contaminants of bacterial origin are probably negligible for 

 present purposes as indicated by the data given in Table I. For proof that our prin- 

 cipal findings reflect genuine properties of viable phage particles, we rely on some 

 experiments with inactivated phage cited at the conclusion of this paper. 



The Chemical Morphology of Resting Phage Particles.— Anderson (1949) 

 found that bacteriophage T2 could be inactivated by suspending the particles 

 in high concentrations of sodium chloride, and rapidly diluting the suspension 

 with water. The inactivated phage was visible in electron micrographs as tad- 

 pole-shaped "ghosts." Since no inactivation occurred if the dilution was slow 



TABLE I 



Composition of Ghosts and Solution of Plasmolyzed Phage 



Per cent of isotope] 



Acid-soluble 



Acid-soluble after treatment with DNase 



Adsorbed to sensitive bacteria 



Precipitated by antiphage 



Whole phage labeled with 



pj2 



S»s 



1 



85 

 90 



1 

 90 

 99 



Plasmolyzed 

 phage labeled with 



P" 



1 



80 



2 

 5 



S»5 



1 

 90 

 97 



he attributed the inactivation to osmotic shock, and inferred that the particles 

 possessed an osmotic membrane. Herriott (1951) found that osmotic shock 

 released into solution the DNA (desoxypentose nucleic acid) of the phage 

 particle, and that the ghosts could adsorb to bacteria and lyse them. He pointed 

 out that this was a beginning toward the identification of viral functions with 

 viral substances. 



We have plasmolyzed isotopically labeled T2 by suspending the phage 

 (10" per ml.) in 3 m sodium chloride for 5 minutes at room temperature, and 

 rapidly pouring into the suspension 40 volumes of distilled water. The plas- 

 molyzed phage, containing not more than 2 per cent survivors, was then an- 

 alyzed for phosphorus and sulfur in the several ways shown in Table I. The 

 results confirm and extend previous findings as follows: — 



1. Plasmolysis separates phage T2 into ghosts containing nearly all the 

 sulfur and a solution containing nearly all the DNA of the intact particles. 



2. The ghosts contain the principal antigens of the phage particle detect- 

 able by our antiserum. The DNA is released as the free acid, or possibly linked 

 to sulfur-free, apparently non-antigenic substances. 



89 



