VIRAL FUNCTIONS: ORDER AND DISORDER 



infection the genetic material of the bacteriophage starts multi- 

 plying. After 12 to 20 minutes, the phage DNA is condensed into 

 a ball, and the subunits of the head are assembled around the ball 



<v/w» genetic material of the bacteriophage 

 — phage proteins • endolysine 



Figure 26. The Life Cycle of a Bacteriophage. 



1. Infection: (a) the bacteriophage particle has attached onto the receptive 

 bacterium; (b) it has injected its genetic material into the bacterium. 



2. Beginning of the vegetative phase: Phage proteins are produced, and the 

 autonomous multiplication of the phage genetic material is initiated. The 

 bacterial chromosome c is disintegrating. 



3. The bacterial chromosome has disappeared. Its building blocks (nucleic 

 bases) will be incorporated in the phage genetic material. More phage material 

 has been synthesized. 



4. The proteins are organized around the folded genetic material, and phage 

 particles are formed. A lytic enzyme (endolysine) will be produced by the 

 vegetative bacteriophage. The bacterial wall will be hydrolyzed and the bac- 

 terium will l)-se, thus liberating the bacteriophage particles. 



of nucleic acid. Finally, by a process that is not understood, the tail 

 appears \yhere it should appear. The infectious particle is formed. 

 In the meantime, a peculiar phage protein has been produced, the 

 endolysine, \yhich in the particle \vill be localized at the tip of the 

 tail. This endolysine depolymerizes the mucopolysaccharides of the 

 bacterial wall. The bacterium is lysed and liberates some hundred 



[67] 



