(A) Structures of PA siderophores pyochelin and pseudomonine, and antimicrobial siderophore ferrocin. Putative iron-binding atoms are colored red, and fatty acid tails, in blue. (B) Structure of promysalin with proposed iron contacts shown in red (left), minimized calculated structure (middle), and CAS agar plate (right). Captions indicate the concentration of promysalin (mM) in 10 μL innoculations on CAS agar, with EDTA (6 mM) and DMSO (10% v/v) as controls.