In Bacillus cereus purine ribonucleosides and deoxyribonucleosides share a common inducible catabolic pathway, leading to the formation of ribose-5-P or deoxyribose-5-P respectively inside the cell, while the purine ring remains in the external medium. Both ribo- and deoxyribonucleosides are inducers of adenosine deaminase, inosine-guanosine phosphorylase and phosphopentomutase, the enzymes of the catabolic pathway. We now show that deoxyribonucleosides, but not ribonucleosides, induce the aldolase specific for deoxyribose-5-P (2-deoxy-D-ribose-5-phosphate acetaldehyde lyase, EC 4.1.2.4), thus allowing the sugar moiety of exogenous deoxyribonucleosides to be utilized as an energy source.