48 



Essays in Biochemistry 



minutes after the resuspension of a centrifuged bacterial colony yields 

 erratic results due to clumping of cells. However, the cell count re- 

 mains constant from one-half hour to 6 hours, and longer, on methio- 

 nine starvation, and, therefore, the increase in acid-soluble material 

 and in RNA which continue significantly after the first hour represents 



100 



60 



dn 40 



20 



KEY 

 I Acid wash 

 H3RNAP 

 DNAP 





1 

 i 



Fig. 8. 



12 3 4 5 6 



Hours of starvation 



Relative changes in nucleic acid content on methionine starvation of 

 E. coli K 12 W-6. 



unequivocally an increase of these components within each starved cell. 

 The large increase in nucleic acid material without increase in the 

 number of viable cells in these starving cultures was confirmed by a 

 simple independent method. A 10-ml. aliquot containing 2.8 X 10 8 

 cells per milliliter at the start of the starvation was centrifuged, washed, 

 resuspended in 10 ml. of fresh medium, and the cell suspension was 

 exposed to ultrasonic vibration for 10 minutes. The optical density 

 at 260 in/*, of the resulting clear fluid was 0.8. After 4 hours of starva- 

 tion an identically treated aliquot yielded an optical density of 1.2, 

 or an increase of 50%. n 



