DORMANCY OF BACTERIAL ENDOSPORE 91 



B. subtUis while ours came from B. cereiis. We are inclined not 

 to believe this, partly from the fact that the L-alanine dehydro- 

 genase from B. cereus seems identical to the one described by 

 Pierard and Wiame"*^ in B. subtiUs vegetative cells and also the 

 evidence available with B. cereus indicates a similarity with the 

 previous work on B. subtiUs. 



In considering the specificity of the initial interaction in 

 germination, one point we must carefully keep in mind — that 

 there are probably several alternate ways to initiate germination. 

 Thus for example, L-alanine can be replaced by glucose for the 

 germination of many species of spores. Also, the initial stages in 

 germination involve a degradation of the exosporium liberating 

 among other components L-alanine. This can be seen by blocking 

 overall germination with arsenite and showing a release of 

 endogenous alanine following exposure to exogenous L-alanine. 

 Alanine liberated thus could act as an endogenous germinating 

 agent, this germination being inhibited by D-alanine. Possibly 

 this may be the mechanism of action of /i-alanine — acting as a 

 stimulant for L-alanine liberation. 



The effect of these agents can be interpreted therefore in 

 terms of the model shown in Fig. 8. The arguments supporting 

 the L-alanine dehydrogenase as the initial binding site can be 

 summarized as follows: 



1. Alanine deamination is an essential but not sufficient step 

 for germination; 



2. Activation parallels activation for germination; 



3. NH3 release parallels germination; 



4. The conditions for optimal enzyme activity (high pH) are 

 consistent with those for optimum germination; 



5. Both the enzyme and germination are inhibited by d- 

 amino acids, especially alanine; 



6. There is a parallel specificity between enzyme and germina- 

 tion. 



References p. 94 



