118 G. G. KRISHNA MURTY 



Following Dr. Foster's work, I extracted some B. terminalis spores with 

 1 A^ sulfuric acid for 17 hours at room temperature. Assay of the resulting 

 supernatant fluid showed that some ninhydrin positive material had been 

 removed, as well as dipicolinic acid corresponding to 10% of the original 

 dry weight of the spores. 



This treatment killed the spores; that is, they would not now form colonies 

 nor germinate with L-alanine and adenosine using the optical procedure. 

 However, the treated spores retained 50% of their initial adenosine ribosi- 

 dase activity. This remaining activity was no longer resistant to heat; after 

 30 minutes at 100°C the activity decreased from a Q of 5 to a Q of 0.6 

 micrograms ribose produced per mg spores per minute. This should be 

 compared to the heat resistance of the enzyme in untreated spores, which 

 retains nearly full activity after 30 minutes at 100°C. 



Two things had been done to the spores by the acid treatment: practically 

 all of the dipicolinic acid was removed, and heat resistance of the adeno- 

 sine ribosidase was eliminated. 



Harlyn Halv ORSON: The rapidity and specificity of the germination re- 

 quirements suggest a trigger mechanism for the breaking of dormancy. As 

 has been previously indicated, germination is associated with a burst of 

 enzymatic activity from DPN- and TPN-linked dehydrogenases as well as 

 ATP-linked kinases and probably ADP-linked energy yielding reactions. One 

 attractive regulatory mechanism to control their activities could be the fol- 

 lowing: If these cof actors were entirely present in the dormant spore in the 

 form of DPNH, TPNH and ATP, respiratory activity could be suppressed 

 due to a lack of H acceptors for the dehydrogenases and to a deficiency in 

 phosphate acceptors (ADP). Heat activation or the proper addition of ger- 

 mination requirements may enable the oxidation of DPNH and TPNH and 

 the hydrolysis of ATP. I wonder if Dr. Powell would like to comment on 

 this. 



SUSSMAN: In response to the points raised by Dr. Halvorson, I'd like to 

 say that the dormant ascospores of that ubiquitous and fascinating organ- 

 ism, Neurospora, contain more ATP than any fungal cell of my acquaint- 

 ance. On the other hand, as soon as the spores are activated there is a pre- 

 cipitous decline in ATP accompanied by an approximately stoichiometric 

 rise in ADP concentration. This is interesting in view of what Dr. Hal- 

 vorson said about a compound associated Avith energy transactions being 

 "plugged in," as it were, into the manifold jobs of the cell at the time when 

 it is needed most. There seems to be definite selective advantage in an ar- 

 rangement like this that mobilizes such substances for use when dormancy 

 is broken. The second point I should like to make is concerned with the 

 very interesting series of four papers we are discussing. It looks more and 



