Many bacteria synthesize and secret iron-binding small molecules termed siderophores to obtain iron under iron-limiting conditions. Enterobactin is a prime example of a catechol-containing siderophore produced by gram-negative enteric bacteria such as Escherichia coli and Salmonella typhimurium. With a KD of 10-49 M for hexadentate coordination of Fe3+, enterobactin appears admirably engineered for removing ferric iron from vertebrate proteins such as transferrin during infection. However, the mammalian proteins serum albumin and lipocalin 2 bind iron-free and iron-bound enterobactin, respectively, thereby suppressing bacterial growth in various mammalian microenvironments. Pathogenic bacteria have evolved the iroA cluster (containing five genes, iroB, C, D, E, N) to counteract the host innate immunity mediated mostly by lipocalin 2. In this talk, I will discuss the biochemical actions of proteins in the iroA cluster, and how they help the pathogenic bacteria to win the battle for iron.