33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 



235 



IV. Nucleic Acids of Temperate Bacteriophages 

 1. The Lysogenic State 



The viruses of the T series are all members of the "virulent" class of 

 bacteriophage. These bacteriophages — and many others which prey upon 

 a wide range of bacterial species — kill the host cells which support then- 

 replication. An entirely different type of parasitic relationship can be es- 

 tablished by the members of another large class of bacteriophage, the 

 "temperate viruses." 



Upon infection of a susceptible bacterial culture by a temperate phage 

 stock, a portion of the infected cells will be invaded and lysed as by the 

 virulent phage. However, in another portion, which may under appropriate 

 circumstances be much the larger portion, a different relationship is es- 

 tablished. At some time after invasion, a genetic element carrying at least 

 the hereditary characteristics of the parental phage particle is added to 

 the genetic complement of the infected bacterial cell (or one of its progeny). 



io-2 



io- J 



20 40 60 80 



UV DOSE (seconds) ON CELLS 



Fig. 7. Apparent survival of ultraviolet irradiated Tl • ) and T3 (O) phage upon 

 ultraviolet irradiated host cells as a function of the dose administered to the cells. 

 [From E. S. Tessman, Virology 2, 679 (1956).] 



