Illustration of a ferric enterobactin receptor from the bacterium Pseudomonas aeruginosa embedded in a lipid bilayer membrane. This receptor aids the transport of siderophores (iron-carrying compounds) across the bacterial cell membrane. Siderophores are being investigated as a 'Trojan horse' strategy to facilitate the uptake of antibiotics by bacteria. The antibiotic, bound to a siderophore molecule, would be transported into the cell by enterobactin receptors.