Did you know there’s a war going on in your body, right now? It’s all about getting and hoarding Iron.

A Siderophore “iron carrier” Iron(III) Siderophore ready for transport

It’s an arms race between the mammalian immune system and bacteria in the search for iron: a) enterobactin removes iron from transferrin b) siderocalin intercepts the ferric complex of enterobactin c) bacteria produce alternative siderophores such as salmochelin. salmochelin enterobactin siderocalin transferrin

Anthrax siderophores siderocalin Fe-enterobactin “Bacterial-Host Iron Wars” BERKELEY – University of California, Berkeley Bacteria need iron to grow. In iron-poor microenvironments, biosynthetic genes to make, secrete, and retrieve siderophores Siderophores scavenge ferric iron from the environment. Mammalian hosts fight back They sequester iron in serum via serum albumin and siderocalin. virulent bacteria counterattack by an unusual enzymatic C- glycosylation of the enterobactin scaffold, generating salmochelins (first detected in virulent salmonella) bulky glucosyl moiety prevents sequestration of this tailored siderophore by siderocalin, allowing retrieval of the iron-loaded form by the bacteria. Anthrax bacteria require two siderophores working by two different mechanisms. Siderocalin, the human immune protein, binds the anthrax bacillibactin siderophore and effectively sidelines it. a second "stealth" iron scavenger, petrobactin, to get around the human defense against the first scavenger. Petrobactin is not bound by siderocalin.

Why do we need all that Fe? Hemes in Hemoglobin and Cytochromes