212 BACTERIOPHAGES 



little or no degradation of the protein of infecting phage particles 

 during the infectious process. 



In contrast to these conclusions are those of Kozloff (1952a,b) 

 which are based on experiments with N^Mabeled T2 phage. 

 Kozloff concluded that "up to 80 per cent of the parent virus 

 DNA and protein was extensively broken down to a variety of 

 small fragments during virus reproduction." Actually these 

 papers give no experimental evidence that the virus protein was 

 broken down. 



b. Breakdown of Phage Nucleic Acid Following Superinfection 



The work of Hershey and Chase (1952) demonstrated that 

 shortly after phage adsorption the bulk of the phage nucleic acid 

 enters the bacterial cell. There seems to be general agreement 

 that some of this nucleic acid is broken down to very small frag- 

 ments during intracellular phage growth. The first indication 

 of the extent of this degradation is in a paper of Putnam and 

 Kozloff (1950). Purified labeled T6 phage was used to infect 

 bacteria at a multiplicity of 3, and after bacterial lysis the lysate 

 vvas fractionated to determine the distribution of the P^- label. 

 About 10 per cent of the P^^ was found in the bacterial debris, 

 40 per cent in the purified phage progeny, and 50 per cent failed 

 to sediment at 20,000 X g for 2 hours. In another experiment 

 in which the lysate was fractionated by means of a Sharpies 

 supercentrifuge 57 per cent of the P^^ was found in the effluent. 

 On further fractionation of the effluent, 26 per cent of the initial 

 phage P^^ was recovered in acid-soluble form. Of this about half, 

 or 13 per cent of the initial phage P^^, was inorganic phosphate. 

 Essentially the same distribution of P^- was found whether the 

 multiplicity of infection with labeled phage was 1 or 3. 



The next important development was the investigation of the 

 kinetics of release from infected bacteria of trichloroacetic acid- 

 soluble phosphorus derived from the infecting phage. This 

 work led to the discovery that a considerable part of the P*- of 

 phage T2 may be liberated within a few minutes of the time of 



