38 



Essays in Biochemistry 



change in aptitude. A diminished rate of metabolism at the time of 

 irradiation, whether induced by chilling or by a metabolic inhibitor, 

 was thus ruled out as a possible source of inaptitude. 



Next to be explored was the possibility that something accumulates 

 during the aberrant metabolism of starvation which somehow inhibits 

 the lysogenic response. To test this possibility the methionine-requir- 



i — + Methionine 



Minutes 



Fig. 1. The effect of starvation prior to irradiation on the lysogenic response. 

 Curve 1 = E. coli K 12 W-6 in logarithmic growth phase. Curve 2 = same after 

 induction by ultraviolet. Curve 3 = the organisms irradiated after 3 hours of 

 starvation of methionine. The amino acid was, of course, added, after the 



irradiation. 



ing auxotroph E. coli K 12 W-6 at a concentration of 10 9 cells per milli- 

 liter was subjected to methionine starvation for 3 to 4 hours. After 

 the starvation, the starved organisms were eliminated from the medium 

 by high-speed centrifugation or by sterile filtration. Wild type of 

 E. coli K 12 in logarithmic growth phase, i.e., with full aptitude, were 

 harvested and suspended to a concentration of 10 8 cells per milliliter 

 in the same sterile filtrate in which the auxotrophs had starved. Such 

 a filtrate should have been an adequate culture medium for the wild 

 type of organism. Indeed, that is precisely the medium on which the 

 wild type of organism is grown. However, even after an immersion 

 of only ") minutes, the minimum time dictated by the technique, the 



