Small-angle neutron scattering (SANS), cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) were used to study the metal-dependent phase behavior of microbially produced surfactantsmarinobactins B, D, and E (M-B, M-D, and M-E). Marinobactins A-E are siderophores that facilitate Fe(III) acquisition by the source bacterium through the coordination of Fe(III) by the peptidic headgroup. All of the marinobactins have the same six amino acid headgroup but differ in the length and saturation of the monoalkyl fatty acid tail. Fe(III) coordinated to M-E (Fe(III)-M-E) was found to form micelles with a diameter of similar to 3.5 nm that underwent a supramolecular transformation to produce a monodisperse population of vesicles with an average diameter ranging from similar to 90 to 190 nm upon addition of Cd(II), Zn(II), or La(III). SANS profiles of the transition-metal-induced phase exhibit a Bragg peak at Q(B) approximate to 0.11-0.12 angstrom(-1) and were fit to a SANS model for multilamellar vesicles that have an interbilayer repeat distance of 2 pi/Q(B) approximate to 5.6-5.0 nm. Cryo-TEM images of the Zn(II)-induced phase reveals the presence of similar to 100 nm diameter approximately spherical aggregates of uniform electron density. The temperature dependence of the Zn(II)-induced transformation was also investigated as a function of the length and degree of unsaturation of the Fe(III)-marinobactin fatty acid tail. The Cd(II)-, Zn(II)-, and La(III)-induced phase changes have features that are similar to those of the previously reported Fe(III)-induced micelle-to-vesicle transition, and this observation has opened questions regarding the role that Cd(II) and Zn(II) may play in bacterial iron uptake.