BMC Genomics 2006, 7:21 http://www.biomedcentral.com/1471-2164/7/21 FCiogmurpear6ative analysis of the DtxR regulons of sequenced corynebacterial species Comparative analysis of the DtxR regulons of sequenced corynebacterial species. (A) Deduced consensus sequences of DtxR binding sites represented by sequence logos. (B) Comparative content analysis of DtxR binding sites belonging to the DtxR regulon. The Venn diagrams show the number of shared and species-specific DtxR binding sites among the genomes of C. glutamicum (Cg), C. efficiens (Ce), C. diphtheriae (Cd), and C. jeikeium (Cj). tive genes, it is generally ensured that the genes fall under direct regulation by the DtxR protein and that the bacte- rium can benefit from the acquired genetic information. The close functional relationship between DNA binding sites of at least DtxR and IdeR is indeed apparent from the observation that the regulatory proteins can interact with operators of the cognate regulons in either corynebacteria or mycobacteria [48]. Conclusion In summary, the presented experimental work adds con- siderably to our currrent understanding of the transcrip- tional regulatory network of C. glutamicum genes that are controlled by the diphtheria toxin repressor homolog DtxR and of the response of this bacterium to changing environmental iron levels. The results demonstrate that DtxR acts as a dual transcriptional regulator with a major role in controlling the expression of genes involved in iron metabolism. The DtxR protein exerts its dual regula- tory function as repressor of genes participating in iron uptake and iron utilization and as activator of genes responsible for iron storage and DNA protection. Moreo- ver, the data suggest that the DtxR protein acts as global regulator by controlling the expression of other regulatory proteins that might take care of an iron-dependent regula- tion of a broader transcriptional network of C. glutamicum genes. Methods Bacterial strains and growth conditions Wild-type strain C. glutamicum ATCC 13032 (American Type Culture Collection, Manassas, VA) was used to char- acterize the DtxR regulon. C. glutamicum strains were rou- tinely grown at 30°C in Luria-Bertani medium [49]. Growth of C. glutamicum strains in CGXII minimal medium [50] containing 30 mg/l protocatechuic acid was monitored in time intervals of 1 h with the nephelometer Nephelostar Galaxy (BMG Laboratories, Offenburg, Ger- Page 15 of 19 (page number not for citation purposes)