62 CLARENCE F. SCHMIDT 



Table X 

 Inhibition by D-amino acids 



— = No inhibition + = Inhibition 



even the spontaneous germination appears to be somewhat inhibited by D- 

 serine. 



Table IX shows some experiments on what I have termed cross-blocking 

 by D-amino acids. In these tests L-alanine, L-valine and ^-alanine have been 

 used as activators with D-alanine, D-valine and D-serine as inhibitors. It 

 may be seen that neither D-valine or D-serine inhibit the activation by L- 

 alanine, all three D-amino acids inhibit activation by ^-alanine, while D- 

 alanine and D-serine inhibit activation by L-valine. 



Table X summarizes the inhibiting effect of D-amino acids for both spore 

 suspensions. The dz symbol is used with both the L-alanine — D-alanine and 

 L-valine — D-valine systems since it was shown that these inhibitions were 

 overcome on prolonged incubation. It also been found that D-alanine, but 

 not D-valine or D-serine, inhibits the chemical activation produced by the 

 DT+ST medium. This result, together with the fact that neither D-valine 

 or D-serine inhibits L-alanine, may suggest that the chemical activator in 

 the DT+ST medium is L-alanine. Also, as is shown in this table, the D- 

 amino acids fail to inhibit the development of heat activated spores on the 

 basal 5.504 medium, suggesting that the mechanism of heat activation is dif- 

 ferent from and unrelated to the mode of activation by L-amino acids. 



In addition to activation by heat, a further phenomenon of interest is the 

 deactivation which may occur during the storage of heat-activated spores. 

 This was first pointed out by Curran and Evans in 1946. They found that 

 spores of several members of the genus Bacillus were activated by preheating 

 and that a substantial proportion lost activation and were apparently non- 

 viable following storage at 98°F. Post-storage preheating led to partial 

 or complete reactivation, depending upon the culture used. Preheating and 

 storage in distilled water had a different effect on activation and deactiva- 

 tion than similar treatment in 1% glucose solution. 



Table XI shows some results upon the deactivation following preheating 



