The Biochemistry of Lysogeny 37 



this point. He said that biochemists should strive to be biologists as 

 well as chemists to justify their special designation, for, whereas the 

 chemist is best provided with the machinery for the cultivation of the 

 borderland frontier between chemistry and biology, it is the biologist 

 who best knows the lay of the land. 



The next best thing to becoming a biologist is to stick close to one. 



Lwoff observed very early that the physiological condition of the 

 lysogenic organism at the time of irradiation determined the extent of 

 the lysogenic response. Organisms which were on a glucose starvation 

 regimen prior to the irradiation seemed to have acquired a resistance 

 to the irradiation. Whereas in logarithmic growth phase only 1% of 

 lysogenic Escherichia cull K 12 will survive a given dose of irradiation 

 as colony formers, about 75^ of the same organisms will survive the 

 same dose if the organisms are deprived of glucose for 3 hours prior 

 to the irradiation. The yield of free phage is, of course, proportionally 

 diminished. The organisms have become "inapt." The acquisition of 

 inaptitude by starvation is general for all inducible lysogenic organ- 

 isms, nor is it restricted to glucose starvation. Nitrogen or specific 

 amino acid starvation in the presence of ample glucose confer inapti- 

 tude on lysogenic organisms as well.' 1,4 A typical experiment on the 

 development of inaptitude on methionine starvation in a lysogenic, 

 methionine-requiring auxotroph, E. coli K i2 W-6 (isolated by Dr. 

 J. Lederberg), is given in Fig. 1. 



Inaptitude, though it is only a peripheral problem related to lysog- 

 eny, can be submitted to chemical scrutiny. The known effects of 

 starvation could be probed seriatim as possible sources of inaptitude. 

 In turn, should the search for the mechanism of inaptitude be success- 

 ful, the findings might not be without bearing on the mechanism of 

 induction, the ultraviolet-irradiation-induced proliferation of the other- 

 wise stable prophage. For often, an understanding of a block to a 

 biochemical mechanism has been revealing of the mechanism itself. 



With this, perhaps naive, overall plan in mind, some experiments 

 were devised. In the first place we had to explore, and preferably rule 

 out, the unfruitful possibility that inaptitude is merely the result of 

 the diminished metabolism of starvation. E. coli Ki^ in logarithmic 

 growth phase was rapidly chilled to 3°C, kept at that temperature for 

 as long as 20 hours, and then subjected to a normal inducing dose of 

 irradiation at 3°. When they were returned to the warm room such 

 cultures gave the usual lysogenic response. Cultures whose growth was 

 inhibited by an antimetabolite, such as ethionine, also showed but little 



