54 VIRAL PROTEIN AND NUCLEIC ACID IN BACTERIOPHAGE GROWTH 



These properties show that T2 inactivated by formaldehyde is largely in- 

 capable of injecting its DNA into the cells to which it attaches. Its behavior in 

 the experiments outlined gives strong support to our interpretation of the cor- 

 responding experiments with active phage. 



DISCUSSION 



We have shown that when a particle of bacteriophage T2 attaches to a 

 bacterial cell, most of the phage DNA enters the cell, and a residue contain- 

 ing at least 80 per cent of the sulfur-containing protein of the phage remains 

 at the cell surface. This residue consists of the material forming the protective 

 membrane of the resting phage particle, and it plays no further role in infec- 

 tion after the attachment of phage to bacterium. 



These facts leave in question the possible function of the 20 per cent of sul- 

 fur-containing protein that may or may not enter the cell. We find that little 

 or none of it is incorporated into the progeny of the infecting particle, and that 

 at least part of it consists of additional material resembling the residue that 

 can be shown to remain extracellular. Phosphorus and adenine (Watson and 

 Maal0e, 1952) derived from the DNA of the infecting particle, on the other 

 hand, are transferred to the phage progeny to a considerable and equal ex- 

 tent. We infer that sulfur-containing protein has no function in phage multi- 

 plication, and that DNA has some function. 



It must be recalled that the following questions remain unanswered. (1) 

 Does any sulfur-free phage material other than DNA enter the cell? (2) If 

 so, is it transferred to the phage progeny? (3) Is the transfer of phosphorus (or 

 hypothetical other substance) to progeny direct — that is, does it remain at 

 all times in a form specifically identifiable as phage substance — or indirect? 



Our experiments show clearly that a physical separation of the phage T2 

 into genetic and non-genetic parts is possible. A corresponding functional 

 separation is seen in the partial independence of phenotype and genotype in 

 the same phage (Novick and Szilard, 1951; Hershey el al., 1951). The chemi- 

 cal identification of the genetic part must wait, however, until some of the 

 questions asked above have been answered. 



Two facts of significance for the immunologic method of attack on problems 

 of viral growth should be emphasized here. First, the principal antigen of the 

 infecting particles of phage T2 persists unchanged in infected cells. Second, it 

 remains attached to the bacterial debris resulting from lysis of the cells. These 

 possibilities seem to have been overlooked in a study by Rountree (1951) of 

 viral antigens during the growth of phage T5. 



SUMMARY 



1. Osmotic shock disrupts particles of phage T2 into material containing 

 nearly all the phage sulfur in a form precipitable by antiphage serum, and 

 capable of specific adsorption to bacteria. It releases into solution nearly all 



102 



