340 



B. Magasanik, et al. 



energy. The effect of these restrictions on the formation of 

 protein, RNA and deoxyribonucleic acid (DNA) during the 



1.5 



i.O 



1.5 



1.0 



2.0 

 1.5 

 1.0 



\ \ r 



Initial 

 RNA/PROT Arginine - limited 



0.550 



1 



Final 

 RNA/PRof 

 ,DNA 

 PROT 

 RNA 0.510 



Guanine -limited 



0.430 



0.289 



Glucose -limited 



..,— DNA 



0.528 



0.370 



■*PPOT 



♦- -• RNA 



50 100 



TIME (minutes) 



150 



Fig. 1. The relative increases of DNA, RNA, and protein 

 in cultures of Aerobacter aerogenes, strain 5-P-14, entering 

 the maximum stationary phase because of limiting 

 amounts of arginine, guanine, or glucose. Log phase cells 

 were inoculated into the basal salt medium (Magasanik, 

 Brooke and Karibian, 1953) containing the following com- 

 pounds either in excess or limiting concentrations : glucose 

 (0-2 per cent or 0-025 per cent), guanine (50 jJ-g./ml. or 

 5 [i.g./ml.), and arginine (100 |jLg./ml. or 10 [xg./ml.). The 

 cultures were incubated aerobically at 37° and samples 

 were taken at different times and analysed for RNA, DNA 

 and protein by standard colorimetric procedures. The re- 

 lative increases in these components are plotted against 

 time, beginning when growth ceased to be exponential. 

 The numbers to the left of the curves are the RNA: 

 protein ratios at this time ; the numbers to the right of the 

 curves are the RNA : protein ratios of the final samples. 



passage of the cell from the exponential to the stationary 

 phase of growth is shown in Fig. 1. It can be seen that the 

 lack of arginine affects equally the rates of formation of the 



