CHAPTER XIV 



NUTRITIONAL AND METABOLIC 

 REQUIREMENTS FOR PHAGE PRODUCTION 



The nutritional requirements for phage production are con- 

 siderably more complex than are, for instance, the requirements 

 for bacterial multiplication. How complex they seem depends 

 on our frame of reference and on the operational methods used. 

 The nutritional requirements for phage reproduction will be 

 quite different whether one considers the intracellular vegetative 

 phage, the infected bacterium, or the mixture of free phage and 

 uninfected bacteria to be the reproducing unit. In the latter 

 case one has to consider requirements for adsorption as well as 

 sources of food. If the infected bacterium is the unit under con- 

 sideration, the nutritional requirements are in general the 

 same as those of the host cell alone in the same environment be- 

 cause the infected cell is synthesizing chemically similar proto- 

 plasm using the same enzymes as are used by the uninfected cell. 

 A few exceptions to this generalization will be noted below. If 

 the intracellular phage particle is considered as the reproducing 

 unit, the nutritional environment must include all the chemical 

 elements, amino acids, and nucleotides that go to make up the 

 particle because the phage particle is incompetent to synthesize 

 these substances for itself. If one uses isotopic labels to determine 

 the ultimate source of nutrients, further refinement is possible. 

 One can, for instance, allocate the source of some of the phage 

 phosphorus to the infecting phage particle, some to the bacterial 

 host before infection, and some to the extracellular environment 

 after infection. These various aspects of phage nutrition will be 

 considered in what is hoped will be a logical fashion. Certain 

 points of view with respect to phage nutrition have been pre- 



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