INACTIVATION OF BACTERIOPHAGES BY DECAY OF 

 INCORPORATED RADIOACTIVE PHOSPHORUS* 



By GUNTHER S. STENT and CLARENCE R. FUERST| 



{From the Virus Laboratory , University of California, Berkeley) 



(Received for publication, September 29, 1954) 



It was observed by Hershey, Kamen, Kennedy, and Gest (1951) that bacteri- 

 ophages are unstable if they contain radiophosphorus P^'- of high specific ac- 

 tivity. From day to day, progressively decreasing fractions of such popu- 

 lations of radioactive phage are still able to form plaques when plated on a 

 sensitive bacterial strain, and the rate of loss of infective titer depends on the 

 specific activity of the P^' assimilated. It is the purpose of this communi- 

 cation to present experiments in which these observations of Hershey et al. 

 have been extended to the study of the lethal effects of P^^ decay in various 

 strains of bacteriophage at various temperatures and to the examination of 

 some of the biological properties of the inactivated bacteriophage particles. 

 Some of these experiments have already been reported in preliminary form 

 (Stent, 1953 a). 



Materials and Methods 



Bacteriophages Tl, T2, T3, T5, T7, and their host, E. coli B/r, and phage X and 

 its host, E. coli strain K12S, were used in this study. Strain B/r, a radiation-resistant 

 mutant derived from strain B, was kindly supplied to us by Dr. Aaron Novick. 



Glycerol-casamino acid medium refers to a medium devised by Fraser and Jerrel 

 (1953). H medium is a glycerol-lactate medium of the following composition per liter 

 of distilled water: 1.5 gm. KCl, 5 gm. NaCl, 1 gm. NH4CI, 0.25 gm. MgS04-7H20, 

 10"'* N CaCU, 0.07 M sodium lactate, 2 gm. glycerol, 0.5 gm. bacto-peptone Difco and 

 0.5 gm. bacto-casamino acids Difco. H medium contains 6 mg. /liter total phosphorus, 

 of which 5 mg. /liter are supplied by the casamino acids and 1 mg. /liter by the peptone. 

 Control experiments show that this phosphorus is assimilated by cultures of E. coli 

 neither more nor less readily than inorganic phosphate. 



The techniques described by Adams (1950) were employed for the general pro- 

 cedures of bacteriophagy. 



Radiophosphorus was obtained as carrier-free H3P^^04 from the Isotope Division 

 of the Atomic Energy Research Establishment, Harwell, England. Measurements 



* This investigation was supported by grants from the National Cancer Institute 

 of the National Institutes of Health, Public Health Service and The Rockefeller 

 Foundation. 



X Holder of a National Research Council of Canada Special Scholarship. 



Reprinted by permission of The Rockefeller Institute from 



The .Journal of General Physiology, 38 (4), 441-458, 



March 20, 1955. 



280 



