342 



B. Magasanik, et al. 



the result of increased RNA breakdown masking a continued 

 synthesis. For this reason the experiment was repeated, and a 



50 



100 



150 



TIME (minutes) 



Fig. 2. The relative increases of DNA, RNA, 

 protein and optical density in a culture of 

 Aerobacter aerogenes, strain 5-P-14, during a 

 diauxic lag. The cells were grown aerobically 

 at 37° in the basal medium supplemented 

 with guanine (50 {j.g./ml.) and arginine (100 

 jjt,g,/ml.), and containing glucose (0-06 per 

 cent) and wi/o-inositol (0-2 per cent) as major 

 sources of carbon and of energy. The inset to 

 the figures describes the diauxic growth curve 

 of this culture as followed by its optical den- 

 sity at 420 mfjL. During the period included by 

 the dashed lines in the inset, when the culture 

 was adjusting from growth on glucose to 

 growth on w^/o-inositol, samples were taken 

 and analysed by standard colorimetric pro- 

 cedures for RNA, DNA and protein. The 

 results are plotted in the main part of the 

 figure as relative increases in these compo- 

 nents against time. The increases are relative 

 to the values at zero time, shortly prior to the 

 beginning of the diauxic lag. 



small quantity of [8-^*C]guanine was added to the guanine- 

 containing culture at the beginning of the lag phase ; the cells 



