Ribose utilization by the human commensal Bifidobacterium breve UCC2003

Growth of B. breve UCC2003 on ribose leads to the transcriptional induction of the rbsACBDK gene cluster. Generation and phenotypic analysis of an rbsA insertion mutant established that the rbs gene cluster is essential for ribose utilization, and that its transcription is likely regulated by a LacI-type regulator encoded by rbsR, located immediately upstream of rbsA. Gel mobility shift assays using purified RbsRHis indicate that the promoter upstream of rbsABCDK is negatively controlled by RbsRHis binding to an 18-bp inverted repeat and that RbsRHis binding activity is modulated by D-ribose. The rbsK gene of the rbs operon of B. breve UCC2003 was shown to specify a ribokinase (EC 2.7.1.15), which specifically directs its phosphorylating activity towards D-ribose, converting this pentose sugar to ribose-5-phosphate. In order to investigate differences in global gene expression upon growth of B. breve UCC2003 on ribose, or a combination of ribose and glucose, as compared to glucose, DNA microarray experiments were performed. Total RNA was isolated from B. breve UCC2003 cultures grown on ribose, a combination of ribose and glucose, or glucose. All experiments were performed in duplicate. A dye swap was performed in one of the two biological replicates.