BACTEEIOPHAGE AS A MODEL OF HOST-VIRUS RELATIONSHIP 193 



binary fission.^ Binary fission has no meaning at the molecular level. It has a 

 meaning only if one considers either a complex organelle or structm-e or an 

 organism. 



The essence of phage multiplication is also the replication of the nucleic 

 acid. During the vegetative phase, there is an increase of phage material but 

 the nucleic acid and the proteins, so far as we know, do not form an organized 

 structure. What increases is a disorderly mixture of phage constituents. 

 There is nothing that could divide. There is no binary fission in a bacterio- 

 phage. 



4. Microorganisms possess a system of enzymes which convert the potential 

 energy of foodstuffs into the high energy bonds that are needed for biological 

 syntheses, including the production of a specific pattern. This is the "Lipmann 

 system" which is part of the microorganism itself. The Lipmann system is 

 absent in bacteriophage. The energy for the synthesis and production of a 

 specific pattern of phage material is provided by the host cell. 



It is manifest that bacteriophage differs from classic microorganism by an 

 impressive number of essential features. A line of demarcation can be easily 

 drawn between bacteriophage, on the one hand, and microorganisms, that is 

 to say, organisms, on the other hand. One could therefore decide that bacterio- 

 phage is not an organism. If bacteriophage is not an organism, is it a cellular 

 organelle? 



V. Bacteriophage and Cellular Organelles 



A cellular organelle, or simply an organelle, is a dependent part of an 

 organism. The synthesis of the constituents of an organelle — its growth, its 

 replication, its activity — are controlled by the organism as a whole and in 

 turn the organelle, by the products of its metabolism, takes part in the 

 metabolism of the organism. 



In a lysogenic bacterium, the prophage behaves as if it were a bacterial 

 gene. Its rephcation is controlled by the bacterium as a whole and the 

 prophage is known to modify specifically the bacterium. For all practical 

 purposes the prophage behaves as a cellular organelle. It is a dependent part 

 of an organism, and this organism is not the bacteriophage, but the bacterium. 

 Do we have the right to decide that bacteriophage is a cellular organelle? 

 The fact that bacteriophage, at certain phases of its cycle, behaves as a 



^ It is possible that the Watson-Crick double helix of DNA the duplex, functions as 

 a unit in synthetic processes. If so, from a functional point of view, it is a molecule. 

 The duplex nevertheless replicates. In one of the models proposed for its replication, 

 the two members of the pair separate and each one reproduces its "opposite." The miit 

 of information, the ultimate unit from which a double helix is produced, is the individual 

 single helix which does not undergo fission. 



VOL. II — 13 



