100 NORMAN L. LAWRENCE 



Among the enzymes described by Dr. Lawrence as being active in the 

 intact spores, two in particular have received considerable attention — namely 

 the alanine racemase and the nucleoside ribosidase. Besides adequately satis- 

 fying the general criteria suggested for this group of enzymes, they have 

 been shown to have several characteristics in common which may be applica- 

 ble for other enzymes yet to be reported. (1) Each of these enzymes has 

 been demonstrated to occur in much greater amounts in spores than in the 

 homologous vegetative cells. Although some reports have indicated that the 

 vegetative cells of B. cereus were completely devoid of ribosidase activity, 

 we have been able to demonstrate some heat-labile ribosidase in the vegeta- 

 tive cell of B. terminalis (Nakata, 1956). Perhaps this discrepancy could be 

 explained by the difference in the age and species of the cultures used in 

 each case. (2) The racemase, ribosidase, and also the catalase were found 

 to be extremely heat resistant in the intact spores, in germinated spores, and 

 in the spore-free extracts (Stewart and Halvorson, 1953, 1954; Lawrence, 

 1955a,b; Nakata, 1956). In the case of the racemase and ribosidase, the 

 enzymes were observed to be intimately associated with a particulate frac- 

 tion which presumably is responsible for their thermal-resistant properties. 

 Although no particulate fraction has been demonstrated for the heat-stable 

 catalase, it too may be similarly protected with particles of varying magni- 

 tudes so that they are not separable during centrifugation. 



Insofar as the adenosine deaminase is concerned, we have found no con- 

 clusive evidence to place it among the enzymes active in the dormant intact 

 spores. Aside from its being present in large amounts in the vegetative cells 

 as well as in the spores, it is heat sensitive and non-particulate. From the 

 data available, there appears to be no evidence that adenosine deamination 

 occurs in the absence of germination and under conditions where activation 

 of the enzyme in the intact spore is unlikely. 



We have noted that when using fresh spores of B. terminalis no germination 

 is evident during incubation with adenosine alone at 37°C, thus providing 

 a system where the adenosine deaminase could be studied with dormant 

 resting spores (unpublished data). Employing the optimal conditions for 

 the deaminase as reported by Powell and Hunter (1956), we have observed 

 the fate of adenosine using samples of unheated spores, spores heat shocked 

 15 minutes and 60 minutes at 65 °C. The only product of adenosine noted in 

 each case was adenine, indicating the absence of deamination in the dormant 

 intact spores as well as in the heat-treated spores. Subsequent examination 

 of the incubation mixture revealed the absence of germination in all cases. 

 However, deamination of adenosine to inosine was found to occur with 

 aged spores or under conditions favoring germination, thus prompting the 



