REQUIREMENTS FOR PHAGE PRODUCTION 237 



This question should be divided into two parts, one concerning 

 the mature extracellular phage particle, the other involving the 

 intracellular, vegetative phage. The answer may be quite dif- 

 ferent in the two cases. 



a. Lack of Metabolic Enzymes in Mature Phage 



As discussed previously in Chapters X and XI, it is quite 

 possible that phage enzymes are involved in the release of phage 

 nucleic acid from its protein shell, and in the penetration of 

 phage DNA into the host cell. Yet even here there is no certain 

 evidence for the existence of phage enzymes. Far less evidence 

 is available for the participation of phage enzymes in the later 

 stages of phage reproduction. The important work of Hershey 

 and Chase (1952) demonstrated that, following adsorption of 

 phage to the host cell, most of the phage protein remains on the 

 host cell surface while the phage nucleic acid penetrates through 

 the cell wall into the cell interior. Other experiments indicate 

 that about 3 per cent of the total phage protein penetrates into 

 the host cell (Hershey, 1955). The function of this protein is 

 not known but it might be enzymatic. Prior to this work it was 

 commonly assumed that phage infection involved the penetration 

 of the entire phage particle into the host cell where it multiplied 

 in the host cell juices like a miniature bacterium. It is un- 

 doubtedly this concept which induced various workers to search 

 for oxidative and fermentative activities in phage preparations. 



Much of the earlier work on possible metabolic activities of 

 phage particles was reviewed by Bronfenbrenner (1928) who con- 

 cluded that although there was no evidence for an independent 

 metabolism of phage, the question was still open. Bronfenbren- 

 ner attempted to measure COo production by phage in a micro- 

 respirometer using 10^^ particles (about 1 mg.) of phage. Al- 

 though the method was sensitive to 5 /il. of CO2 he was unable to 

 detect any COo production by this relatively large amount of 

 phage. 



A very careful study of the respiratory and fermentative ac- 

 tivities of a resting phage suspension was made by Schiller (1935) 



