ACTIVATORS AND IMIIHITORS OF GERMINATION 57 



By means of preliminary tests, diluted stock suspensions were prepared 

 and standardized to give a mean count of approximately 100 spores per 0.1 

 inl on the DT -f ST agar following a preheat of 15' at 212°F. The incu- 

 bation temperature was 85°F. The standardization to not over 100 colonies 

 per plate and the use of lower incubation temperature were earlier found 

 necessary in order to achieve maximum counts. In all tests, triplicate plates 

 of each variable were poured. Plates were counted daily or at intervals of 

 two or three days. Observations were continued as long as 20-23 days where 

 continually increasing counts indicated. 



Results 



The results to be presented have been gathered over a considerable period 

 of time. Since the incubation periods have not always been equal, it has 

 been necessary, in order to present the results comparatively, to group the 

 data somewhat according to incubation periods. The group periods adopted 

 are 2-3, 5-6. 9-10. 15-17, and 20-23 days. 



Table I shows the results of a heat activation test using both the complex 

 and the synthetic media. On the complex medium 63% of the spores do not 

 require heat activation. On the synthetic medium from 96 to 849r of the 

 spores require heat activation depending upon the length of observation. 

 Since lOO'^r of the spore> germinate and form colonies on the synthetic 

 medium following heat activation, it is shown that the medium is adequate 

 for colony development from a germinated spore. It is apparent, therefore, 

 that chemical activation is taking place in the complex medium. Studies 

 which have been conducted previously by this technique have very probably 

 Tiot measured the full requirements or effects of heat activation or perhaps 

 have been unable to find heat activation because of the chemical activation 

 produced by the plating medium. 



Table II shows the effects of chemical activation in the synthetic medium. 

 The control counts on the basal medium represent the range of 4 control 



Table I 

 Heat aetivation of spore suspension 5230-5 



Medium Mean Spore Count per Plate 



Incubation Time in Davs 

 2-3 .5-6 9-10 ' 15 



DT+ST 

 DT+ST H* 

 5504 ' 

 5504 H* 



* Heat activated spores 



