ROUND TABLE DISCUSSION 215 



Structural aspect to be considered. The various components of 

 a system can of course only interact if they concur in time and 

 within a narrow space. 



Halvorson Jr. : In answer to Dr. Poljakoff-Mayber, we have 

 recently found mitochondrial type particles in vegetative cells 

 of Bacillus. These particles were also present in the spores but 

 they lacked a number of enzymes associated with cytochrome 

 systems. The incomplete particles constitute a functional differ- 

 ence between spores and vegetative cells. I am rather inchned to 

 believe that the differences between spores and sporulating cells 

 must be very subtle, in view of the great similarity between a 

 system going into the dormant state and the dormant state itself. 



Lees: 1 think I mentioned in my lecture that mitochondria 

 which are readily visible in the developing embryo of grass- 

 hoppers, 'disappear' when the embryo goes into diapause. They 

 reappear when it comes out of diapause. 



Mayer: May I enquire what exactly is meant here by dis- 

 appearance and reappearance? 



Lees: My remark was based on the work of Bucklin and his 

 associates who have stained the mitochondria with Janus green 

 B and examined the preparations with the light microscope. 

 Actually, mitochondria are present during diapause but take the 

 stain very lightly, indicating that there is a probable deficiency 

 in the cytochrome system. 



Halvorson Jr. : In spores one observes under the electron 

 microscope particles very similar to those in the vegetative cell. 

 The mitochondria-like particle in the spore is non-functional. It 

 contains several of the enzymes but does not contain a complete 

 oxygen transport system. In the vegetative cell there is a small 

 quantity of the soluble DPNH oxidase. In the spore its quantity 

 is very high and accounts for all of the passage to molecular 

 oxygen. So you employ alternate systems as you go from the 

 spore to the vegetative cell, or the other way. 



Mayer: In seeds, too, one suspects such a switch in electron 

 transport systems with dormancy. It is very pleasing to hear of 

 an even clearer case of it in the bacterial spore. 



