The Biochemistry of Lysogeny 



51 



cells, and the surviving ''biochemical cripples" run the gamut of known 

 and unknown genetic deficiencies. Of course, the captious may argue 

 that there is an equally homogeneous response in such experiments, 

 too, since 99% of the bacteria die. Most likely, however, the cause of 

 their death is not as homogeneous as in induced lysogenic organisms. 



Fig. 9(b). Untreated control at a dilution of 10 — 4 . 



Since the lysogenic response to induction is so uniform the develop- 

 ment of the phage could be more plausibly visualized as resulting from 

 some metabolic shift in a delicately adjusted equilibrium rather than 

 from random lesions in the genetic material. (The profound change 

 in nucleic acid metabolism induced by invasion of external phage, 

 cessation of RNA and increase of DNA synthesis, 13 does not take place 

 during phage development in induced lysogenic cultures. Neither RNA 

 nor DNA synthesis is interrupted after induction by irradiation. 14 ) 



We first considered the possibility that inaptitude results from the 

 loss during starvation of some radiation-sensitive metabolite which is 



