A. D. HERSHEY AND MARTHA CHASE 



53 



bacterial debris. The lysates were fractionated and assayed as described previously, 

 with the results shown in Table VIII. 



The data show that stripping reduces more or less proportionately the S^*- 

 content of all fractions. In particular, the S^^-content of the fraction contain- 

 ing most of the phage progeny is reduced from nearly 10 per cent to less than 

 1 per cent of the initially adsorbed isotope. This experiment shows that the 

 bulk of the S^* appearing in all lysate fractions is derived from the remains of 

 the coats of the parental phage particles. 



Properties of Phage Inactivated by Formaldehyde. — Phage T2 warmed for 

 1 hour at 37°C. in adsorption medium containing 0.1 per cent {v/v) com- 

 mercial formalin (35 per cent HCHO), and then dialyzed free from formalde- 



TABLE VIII 

 Lysates of Bacteria Infected with S^^-Labeled T2 and Stripped in the Waring Blendor 



Per cent of adsorbed S'' or of phage yield: 



Elated in blendor fluid. 

 1st low-speed sediment. 

 2nd " " " . 



High-speed " 



" " supernatant . 



Recovery 93 



Cells stripped 



S« 



Phage 



Cells not stripped 



S" 



86 

 3.8 

 (0.2) 

 (0.7) 

 (2.0) 



9.3 

 11 

 58 



1.1 



79 



39 



31 

 2.7 

 9.4 



(1.7) 



84 



Phage 



13 

 11 

 89 

 1.6 



115 



All the input bacteria were recovered in assays of infected cells made during the latent 

 period of both cultures. The phage yields were 270 (stripped cells) and 200 per bacterium, 

 assayed before fractionation. Figures in parentheses were obtained from counting rates 

 close to background. 



hyde, shows a reduction in plaque titer by a factor 1000 or more. Inactivated 

 phage of this kind possesses the following properties. 



1. It is adsorbed to sensitive bacteria (as measured by either S^^ or P^^ 

 labels), to the extent of about 70 per cent. 



2. The adsorbed phage kills bacteria with an efficiency of about 35 per 

 cent compared with the original phage stock. 



3. The DNA of the inactive particles is resistant to DNase, but is made 

 sensitive by osmotic shock. 



4. The DNA of the inactive particles is not sensitized to DNase by adsorp- 

 tion to heat-killed bacteria, nor is it released into solution by adsorption to 

 bacterial debris. 



5. 70 per cent of the adsorbed phage DNA can be detached from infected 

 cells spun in the Waring blendor. The detached DNA is almost entirely re- 

 sistant to DNase. 



101 



