Enterobactin (Ent)

Enterobactin is a high affinity siderophore that acquires iron for microbial systems. It is primarily found in Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium. Enterobactin is the strongest siderophore known, binding to the ferric ion (Fe3+) with the affinity. This value is substantially larger than even some synthetic metal chelators, such as EDTA.  Enterobactin can extract iron even from the air. Pathogenic bacteria can steal iron from other living organisms using this mechanism, even though the concentration of iron is kept extremely low due to the toxicity of free iron. Iron deficiency in bacterial cells triggers secretion of enterobactin into the extracellular environment, causing formation of an coordination complex "FeEnt" wherein ferric ion is chelated to the conjugate base of enterobactin.