Chemical models of siderophore analogs used in this study. DHB = 2,3-dihydroxybenzoic acid. The TREN (tris(2-aminoethyl)amine) based analogs consist of a TREN backbone, a linker region (gly=glycine, ser = serine, lys = lysine, glu=glutamate, bal= β-alanine) and a CAM (catecholamide) group. TRENmeCAM and TRENbutCAM have additional methyl (me) or butyl (but) groups respectively on the catecholamide ring.