Adenosine deaminase and ribosidase in spores of Bacillus cereus

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Abstract
Disintegrated resting-spore suspensions of B. cereus deaminate adenosine and cytidine, but not adenine, guanosine, guanine or cytosine. These homo-genates also show ribosidase activity towards adenosine and inosine, but not towards guanosine, xanthosine, cytidine or uridine. Deaminase activity is associated with the spore extract and the ribosidase with the spore debris. Adenosine deaminase is heat-stable in intact resting spores, but heat-labile in homogenates and in germinated spores. Ribosidase is heat-stable both in intact and disintegrated spores. Germinated spores showed heat-stable ribosidase activity. Deamination of adenosine is non-oxidative and does not require a cofactor. The ribosidase reaction produces free ribose and no ribose phosphate. The possible relationships between these reactions and germination of B. cereus spores in adenosine are discussed.