Self-assembling amphiphilic siderophores from marine bacteria

Most aerobic bacteria secrete siderophores to facilitate iron acquisition. Two families of siderophores were isolated from strains belonging to two di fferent genera of marine bacteria. The aquachelins, from Halomonas aquamari na strain DS40M3, and the marinobactins, from Marinobacter sp. strains DS40 M6 and DS40M8, each contain a unique peptidic head group that coordinates i ron(III) and an appendage of one of a series of fatty acid moieties. These siderophores have low critical micelle concentrations (CMCs). In the absenc e of iron, the marinobactins are present as micelles at concentrations exce eding their CMC; upon addition of iron(III), the micelles undergo a spontan eous phase change to form vesicles. These observations suggest that unique iron acquisition mechanisms may have evolved in marine bacteria.