TABLE 2.
Siderophores and chelators used in this study
| Siderophore or chelator | Chemical class | Representative producing strain(s)a | pFeb |
|---|---|---|---|
| DHBA | Catechol | Bacillus subtilis 168 strains | ∼15 |
| Bacillibactin | Catecholate | Bacillus subtilis sfp+ strains | 33.1 |
| Enterobactin | Catecholate | Escherichia coli, Salmonella enterica, and other enterobacteria | 34.3 |
| Ferrioxamine b | Hydroxamate | Streptomyces spp., Arthrobacter simplex, Pseudomonas stuzeri, Chromobacterium violaceum, and Hafnia alvei | 26.6 |
| Ferrichrome | Hydroxamate | Ustilago spp., Aspergillus spp., Penicillium parvum, Neovossia indica, and Trichophyton mentagrophytes | 25.2 |
| Coprogen | Hydroxamate | Neurospora crassa, Penicillium spp., curvularia lunata, and Epicoccum purpurascens | 27.5 |
| Schizokinen | Carboxylate/hydroxamate | B. megaterium and Ralstonia solanacearum | NA |
| Arthrobactin | Carboxylate/hydroxamate | Arthrobacter pascens | NA |
| Citric acid | Carboxylate | Bradyrhizobium japonicum | 17.7 |
| EDDHA | Carboxylate | (Ferric chelator) | 26.9 |
a
Adapted from Stintzi and Raymond (60).
b
pFe = (−log[Fe3+] at pH 7.4, [Fe]tot = 1 μM, [L]tot = 10 μM). Values for pFe are from DHBA (estimated from measurements of 2,3-dihydroxy-N,N-dimethylbenzamide [26]), enterobactin and bacillibactin (16), other siderophores (65), citric acid (50), and EDDHA (58; K. Raymond, unpublished data). NA, values not available in the literature.