Cell Division and Protein Synthesis 



Erik Zeuthen 



TJie Biological Insjitiite of the Carhberg Fouiuldtio/i, 

 Copenhagen, Denmark 



I. The synchronized Tetrahymena system 



In the course of the 7 years since Hotchkiss [4] for bacteria and we [10, 

 14] for a protozoon organism {Tetrahymena pxriformis) proposed tempera- 

 ture changes as a tool for phasing or synchronizing cell populations, this 

 field has been rapidlv expanding. 



0.5 



^ 



D.3 



-02 



-0.1 



2 'y 6 8 10 /2 /r f6 /8 20 22 2i 



hours 



Fig. I. The continuous curve represents division inciex, and the broken curve 

 represents cell counts. (From Zeuthen and Scherbaum [14]). 



The synchronous Tetrahymena system is demonstrated in Figs, i and 2. 

 In Fig. I the stippled curve represents the logarithms of the cell counts per 

 ml. During the first 11 hr. growth is at 29" C. which is optimum (28- 

 29° C). We observe first a lag-phase, then a log-phase of growth. During 



