BACTEKIOPHAGE AS A MODEL OF HOST- VIRUS RELATIONSHIP 195 



infection would be the introduction into a cell or an organism of an entity 

 able to multiply, able to produce a disease, and able to reproduce organized 

 infective entities containing proteins and nucleic acid. This definition excludes 

 from infectiousness the transforming principles and the lethal genes which 

 could be introduced from outside. 



Bacteriophage differs from cellular organelles by possessing an infectious 

 phase. Table II clearly indicates that bacteriophage differs by essential 



TABLE II 



Organisms, Viritses, and Cellular Constituents 



Cellular constituents 



Organisms Viruses 



Types of nucleic acid II 



Multiplying as nucleic acid 



and produced from nucleic 



acid only 

 Growth and division ^ 

 Presence of a Lipmann system 

 Infectivity 



" Concerns microorganisms only. The replication of a structure by the template 

 mechanism is considered neither as growth nor as division (see p. 192). 

 * Some organelles only contain a Lipmann system. 



features from organelles as well as from organisms and that it is neither an 

 organelle nor an organism. A bacteriophage is a bacteriophage. What is 

 bacteriophage? 



VI. Bacteriophage as a Virus 



Bacteriophage, being the small and filterable agent of an infectious 

 disease, is classified among viruses. Why? Obviously, because bacteriophage 

 and viruses have a certain number of features in common. Viruses in general 

 are opposed to bacteria, protozoa, fungi, algae, and more generally to micro- 

 organisms. This implies the existence of a category of infectious agents, 

 viruses, which are different from other infectious agents. Viruses are often 

 opposed to microorganisms because of their size. A virus, according to some 

 virologists, should have at least one dimension lower than 200 m/n. If dimen- 

 sions have any meaning, it is not by the astrological virtue of a number, but 

 because of a correlation between size and some essential properties which are 



