42 



H. O. HALVORSON 



morphological changes in the rods which were typical of 

 presporulation. Spores themselves do not actually appear until 

 much later. The actual time of onset of sporulation is shown in 

 Fig. 3. 



8 



12 16 



Time in hours 



Fig. 3. Time of sporulation in active culture of B. cereus T. 



We also investigated the nature of the acids which are 

 released during the early vegetative cell growth and found that 

 only two acids formed, pyruvic and acetic-^. The pyruvic acid 

 appears first and is subsequently converted to acetic acid. This 

 is illustrated in Fig. 4 and 5. These acids appear quite stable 

 during the period of vegetative cell growth, but begin to dis- 

 appear as the pH begins to rise and, presumably it is the 

 oxidation of the acetic acid that creates the high demand for 

 dissolved oxygen just preceding sporulation. Our failure to 

 obtain spores in our initial experiment was because the air 

 supply was not sufficient to satisfy the oxygen demand in this 

 stage of the development of the culture. This difficulty can be 

 overcome in one of two ways; by improving the efficiency of 

 aeration, and by reducing the concentration of the glucose so 

 that less acid is formed and consequently less oxygen is needed. 

 This latter course also reduces the final spore crop. The meta- 

 bolic processes going on during vegetative cell growth must, 

 therefore, be quite different from those which take place in the 



