96 NORMAN L. LAWRENCE 



form. It should be noted that this enzyme has been demonstrated only in 

 extracts of spores of B. terminalis. 



Nucleoside ribosidase. It has been found (Lawrence, 1955; Powell and 

 Hunter, 1956) that spores of a number of species of aerobic bacteria will 

 cleave adenosine and other ribosides, presumably by a hydrolytic process, 

 into the free base and the free sugar. The specificity for nucleosides ap- 

 pears to vary from strain to strain. Strains of B. cereus and B. anthracis 

 attacked adenosine and inosine at equal rates, feebly attacked guanosine, and 

 were inactive toward xanthosine and cytidine. In contrast to this, spores of 

 the terminalis variety of B. cereus attacked adenosine, guanosine, inosine, 

 xanthosine, adenylic acid, cytidine and uridine. It has since been found that 

 2-aminoadenosine and purine riboside are also cleaved, but desoxyinosine, 

 desoxyadenosine, desoxyguanosine and adenine-9-/3-D-glucoside are not 

 (Lawrence, unpublished). 



In all cases, the enzyme was remarkably heat stable, resisting 100°C for 

 an hour or more. Cell free preparations also retained activity. I believe 

 that workers here at Illinois may have further information on cell-free prepa- 

 rations of B. terminalis. 



The role of this enzyme in germination is not clear. It may play an im- 

 portant part in those spores which require adenosine for rapid germination 

 since it has been found that B. terminalis, B. polymyxa, B. anthracis, and B. 

 cereus all possess riboside activity. The enzyme is not present in spores of 

 B. globigii. This species does not require adenosine for rapid germination. 



Other enzymes. Recent work by several people has indicated the presence 

 of other active enzymes in spores. There is a question in my mind as to 

 where to draw the line between dormant and active enzymes in intact spores — 

 heat treatment of spores activates the glucose dehydrogenase system, and 

 apparently these spores are intact, at least they appear so microscopically. 

 Also, mere aging of lyophilized spores alters their response to various germi- 

 nating agents — does this indicate a low level of activity of cellular enzymes? 

 Does this bear any relationship to the proteolytic enzymes of extracts of 

 spores, which were demonstrated by Levinson? Last, I would like to mention 

 diaphorase. apparently found only in spore extracts; and also the oxidation 

 of p-phenylenediamine and hydroquinone, mentioned by Dr. Powell : and the 

 alanine deaminase found by Church. I have no doubt that in the near future 

 spores will be found to possess other active systems also. 



References 



Church, B. D., H. Halvorson, and H. Orin Halvorson. 1954. Studies on 

 spore germination: Its independence from alanine racemase activity. 

 J. Bact. 68: 393-399. 



