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DISCUSSION 



Keynan: Until recently it was assumed that dipicolinic acid 

 was concerned with the regulation of metabolism in the spore 

 stage. But Orin Halvorson reports that dipicolinic acid is not 

 essential at the spore stage, since spores without dipicolinic acid 

 have been obtained by him. They are, however, susceptible to 

 heat. Are we to conclude then that there are several independent 

 mechanisms controlling dormancy, only one of which involves 

 dipicolinic acid. 



Halvorson, Jr. : It all depends on what you call a spore. The 

 structures with a low dipicolinic level, which are not heat 

 resistant and have high respiratory activity are not spores in our 

 view. We never did produce enough of these structures to be 

 able to extract enzymes, but I think they are more activated. As 

 long as no proper study of the kinetics of germination of these 

 structures is possible, we cannot be sure that the results involve 

 any contradiction of the earlier findings. 



