ACTIVATORS AND INHIBITORS OF GERMINATION 69 



yielding reactions were not clearly demonstrated; e.g. in the presence of 

 L-alanine and adenosine. 



In the latter case, these germinating agents can no longer be considered 

 as energetically inactive. Adenosine is at least partially degraded by the 

 action of adenosine deaminase and ribosidase (Powell and Hunter, 1955; 

 and Lawrence, 1955). Also L-alanine is converted to pyruvate which is 

 metabolized via a tricarboxylic acid cycle (Halvorson and Church, this 

 symposium). Several carbohydrates which also serve as germinating agents 

 are actively oxidized. It is therefore likely that other germinating agents 

 may also serve as energy donors. 



Activation, which can lead to spontaneous germination, also results in an 

 activation of endogenous carbon reserves (Murty and Church, this sym- 

 posium). In this case as well, energy requirements for germination may be 

 supplied via endogenous metabolism which can be appreciable under certain 

 circumstances. One might imagine that the failure of energy inhibitors 

 (cyanide, dinitrophenol or azide) to interfere with germination would also 

 argue against such metabolism being involved. However, before interpreting 

 these negative results, I should like to comment on our experience with pyru- 

 vate. At pH 7 pyruvate is not a germinating agent. If one incubates spores 

 Avith pyruvate at pH 4 (where pyruvate is largely undissociated), germina- 

 tion occurs after the pH is raised to 7. The failure of inhibitors at pH 7 to 

 block germination, whereas they are active in inhibiting carbohydrate 

 metabolism in extracts of spores, may merely be due to their failure to enter 

 the spore. The permeability of these agents should be more critically examined 

 in order to interpret the exothermic nature of germination. 



Stumbo : You speak of organisms losing their heat resistance. How much 

 heat resistance do they lose; and, is the transition from a resting state to the 

 lieat-labile state that you refer to an instantaneous thing? Would you not 

 expect to find spores which, shall we say, are half undressed? And maybe 

 if you used, instead of 20 minutes, 30 minutes at 75° or 10 minutes at 75°, 

 you would get a different answer with respect to heat sensitivity. I would be 

 amazed if you didn't. Should this prove to be the case, I think you can 

 expect variations with species. It seems to me you are going to have to 

 define very carefully the time-temperature relationship you are talking about. 

 I think you are going to have to define the relationship with respect to 

 species, and possibly with respect to the history of the spores that you are 

 talking about in order to define heat sensitivity. I can't agree that you can 

 arbitrarily pick 20 minutes at 75° or 20 minutes at 80°, or some other rela- 

 tionship, and say all the spores that resist this are heat stable and all the 

 spores that don't are heat sensitive. I am sure you can find some spores 



