S. SPIEGELMAN AND A. M. CAMPBELL 



The model to be presented is essentially the one designed by 

 Campbell and Spiegelman (10) in an attempt to explain certain 

 paradoxical aspects of the growth kinetics of active particles in 

 long-term adapting stocks. Its major features are most easily 

 seen and developed in terms of "slow" induction. Once these 

 have been exposed, the scheme will be generalized and applied 

 to normal enzyme synthesis. 



The biochemical investigation of the precursor aspect of 

 enzyme synthesis leads to the conclusion that a template is 

 involved. The kinetics of normal induction and the genetic 

 data obtained with the aid of "slow" strains both suggest that 

 induction is characterized in its early stages by an autocatalytic 

 activation. All the data can therefore be described in a unified 

 fashion by the assumption that initially the templates are rel- 

 atively inactive and are autocatalytically converted to full 

 activity during the course of the induction. 



We are thus led to identify the autocatalytic active particle 

 defined by the genetic operations with the autocatalytically 

 activated template demanded by the biochemical studies. 



We now inquire where in our model is the inducer likely to 

 fit and how it is to function. Both kinetic and genetic experi- 

 ments indicate that active templates increase in number during 

 growth in the presence of inducer. Removal of the inducer 

 results in complete cessation of the increase, but the number 

 present at the moment of removal remains constant for many 

 hours. In our opinion the simplest explanation which can be 

 offered to explain this effect is that inducer, or some derivative 

 of it, is irreversibly incorporated into the structure of the active 

 template. If one proceeds along this line of reasoning, one 

 difference between an active template and an inactive one 

 would be that only the former contains galactose. However, if 

 this were the only difference, exposure to galactose should con- 

 vert negative "slow" cells into positive ones, because in one 

 generation half of the templates would have been formed in the 

 presence of galactose. This suggests then that an active tem- 

 plate differs from the inactive form in some property other than 



142 



