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The number of solute-binding protein-dependent transporters in rhizobia is dramatically increased compared with the majority of other bacteria so far sequenced. This increase may be due to the high affinity of solute-binding proteins for solutes, permitting the acquisition of a broad range of growth-limiting nutrients from soil and the rhizosphere. The transcriptional induction of these transporters was studied by creating a suite of plasmid and integrated fusions to nearly all ATP-binding cassette (ABC) and tripartite ATP-independent periplasmic (TRAP) transporters of Sinorhizobium meliloti. In total, specific inducers were identified for 76 transport systems, amounting to approximately 47% of the ABC uptake systems and 53% of the TRAP transporters in S. meliloti. Of these transport systems, 64 are previously uncharacterized in Rhizobia and 24 were induced by solutes not known to be transported by ABC- or TRAP-uptake systems in any organism. This study provides a global expression map of one of the largest transporter families (transportome) and an invaluable tool to both understand their solute specificity and the relationships between members of large paralogous families.

Original publication




Journal article


Proc Natl Acad Sci U S A

Publication Date





17933 - 17938


ATP-Binding Cassette Transporters, Acids, Amines, Amino Acids, Bacterial Proteins, Biological Transport, Carbohydrates, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Genes, Reporter, Molecular Sequence Data, Operon, Plasmids, Promoter Regions, Genetic, Purines, Pyrimidines, Sinorhizobium meliloti