33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 



241 



60 



65 



30 



30 60 90 m 



Fig. 8. Growth (optical density) and RNA and DNA synthesis at 27° after ultra- 

 violet light induction of B. megaterium. [From L. Siminovitch and S. Rapkine, Bio- 

 chim. et Biophys. Acta 9, 478 (1952).] 



Following this block, DNA synthesis resumes and increases exponen- 

 tially achieving a rate greater than is observed in normal cells at the same 

 temperature. 



Since ultraviolet light of comparable dosage is known to block DNA 

 synthesis in some bacteria, 202 • 203 it is questionable whether this block 

 represents a specific consequence of induction. Siminovitch and Rapkine 

 report that a comparable dose to a related nonlysogenic bacterial strain 

 produced no block of DNA synthesis, but the data presented are uncon- 

 vincing. 



It is of interest that exposure of induced lysogenic cells (B. megaterium) 

 to ribonuclease specifically inhibits the synthesis of phage coat protein 

 relative to total protein synthesis. 204 If ribonuclease is added immediately 

 after induction, no phage antigens are ever made although cell growth 

 (turbidity) continues at about one-third the normal rate. If the treat- 

 ment with ribonuclease is delayed for increasing times after induction, 



202 A. Kelner, J. Bacterial. 65, 252 (1953). 



203 D. Kanazir and M. Errera, Cold Spring Harbor Symposia Quant. Biol. 21, 19 

 (1956). 



204 R. Jeener, Biochim. et Biophys. Acta 32, 106 (1959). 



