ACTIVATORS AND INHIBITORS OF GERMINATION 63 



Table XI 

 Spore deactivation following preheating and storage 



Suspension Storage Mean Plate Count 



Temp. °F Storage Time in Days 



5 10 14 



5230-5 



5230-24 



for 15 minutes at 212°F and storage at various temperatures. The suspen- 

 sions were plated both on the DT-f-ST medium and the 5504 medium. No 

 significant differences between the mean counts on the two media were ob- 

 served. Therefore, recovery of the deactivated spores was not improved by 

 the presence of activators in the DT-|-ST medium. In other experiments it 

 also was found that the inclusion of L-alanine in the 5504 medium did not 

 improve recovery of deactivated spores. Plotting the logarithm of the mean 

 spore counts against the time of storage gives an approximately straight line 

 relationship within the limits of accuracy of the few experiments available. 

 A difference may be noted between the two suspensions. With 5230-5, the 

 deactivation at 70°F was much more rapid than at 60° F and 50°F. With 

 5230-24 deactivation at both 70 °F and 60° F was much more rapid than at 

 50°F. Each suspension seems to have its own particular pattern of be- 

 havior. It should also be mentioned that in experiments with both suspen- 

 sions conducted only at 70°F storage, the logarithmic relationship did not 

 seem to hold for storage periods longer than 10-14 days, since a small num- 

 ber, approximately 10% of the population, will continue to germinate even 

 after 20 days' storage. 



These experiments are quite preliminary attempts to establish the pattern 

 of deactivation during storage to serve as a guide to experiments on heat 

 and chemical reactivation. The results, however, together with those of Cur- 

 ran and Evans, seem definitely to contra-indicate the routine preheating 

 prior to storage of suspensions to be retained over a period of time. Pre- 

 heating for activation or for the removal of viable vegetative cells should 

 lie used only where it is a known and controlled variable. 



Discussion 



Dudley S. Titus 



A review of the literature dealing with spore germination stimulants leads 



