THE BACTERIAL ENDOSPORE 



51 



8 



pH 



6- 



4 8 12 



Time in hours 



Fig. 10. The effect of ethyl pyruvate (1.5 10- M) on the pH and sporu- 



lation of a culture of B. cereus T. 



as the other two, probably interferes with the functioning of 

 some enzyme systems rather than with the production of an 

 adaptive enzyme. The ethyl pyruvate acts somewhat differently 

 from the two inhibitors cited above, because in this case the pH 

 rises and stays high. Nevertheless, no spores are formed. We 

 have also investigated the effect of various organic acids upon 

 the reversal of inhibition of these ethyl esters. I am not going to 

 take time to discuss the details of all these experiments, but 

 suffice to say, these inhibitors were reversed by all of the inter- 

 mediates in the glyoxylic acid shunt, but were not reversed by 

 fumarate or other intermediates in the TCA cycle not common 

 to the glyoxylic acid shunt. 



We realize it is dangerous to rely upon inhibitors alone for the 

 verification of a definite pathway in a fermentation, but the 

 circumstantial evidence we had for the involvement of the 

 glyoxylic acid shunt led us to conduct further experiments to see 

 if we could get additional support for this conclusion. We there- 

 fore investigated two other possible inhibitors. If either the 

 TCA or the glyoxylic shunt (the cycles are shown in Fig. 11) is 

 involved, fluoroacetic acid should also be an effective inhibitor, 

 inasmuch as this material interferes with the enzyme that 

 converts citrate to isocitrate. We found this acid to be an 

 effective inhibitor of sporulation. It did not interfere with the 



References p. 59 



