56 H. O. HAL\ ORSON 



TABLE X 



EFFECT OF TIME OF ADDITION ON ETHYL OXAMATE (IQ-- M) ON THE 

 PRODUCTION OF HEAT-STABLE SPORES 



Octyl alcohols-Stable Heat-stable 



Type of culture used ,, , 



cells/ml 



upon the production of heat-resistant spores of B. cereiis. It is 

 to be noted from this that ethyl oxamate interferes with the 

 formation of heat-resistant spores, whether it is added in the 

 beginning to a spore inoculum or an active culture, or before or 

 after the pH has started to rise. If one waits, however, until the 

 pH has gone up to 7.1 or higher, it has no effect. Apparently, by 

 this time, the synthesis of DPA has already progressed to the 

 point where heat-resistant spores can be found. We have 

 examined the inhibited cultures for DPA and find there are very 

 small amounts present. It is to be noted that a few heat-resistant 

 spores are formed, so that the ethyl oxamate does not block the 

 synthesis of DPA completely; but it does interfere with the 

 synthesis sufficiently, so that more than 95 % of the spores that 

 are formed are heat sensitive. The amount of DPA which is 

 found in such preparations is slightly more than one would 

 expect if one assumes that the heat-resistant spores have their 

 normal content, and the heat-sensitive spores, none. It is 

 possible, therefore, that some DPA may be present also in the 

 heat sensitive spores. 



Somewhat similar results are obtained with the diethyl pime- 

 late. This inhibitor, however, interferes with the development of 

 normal vegetative cells if it is added to the culture at time, or 

 very early in the growth of the vegetative cells. The vegetative 



