Iron is necessary for the survival of almost all aerobic organisms. In the mammalian host, iron is a required cofactor for the assembly of functional iron-sulfur (Fe-S) cluster proteins, heme-binding proteins and ribonucleotide reductases that regulate various functions, including heme synthesis, oxygen transport and DNA synthesis. However, the bioavailability of iron is low due to its insolubility under aerobic conditions. Moreover, the host coordinates a nutritional immune response to restrict the accessibility of iron against potential pathogens. To counter nutritional immunity, most commensal and pathogenic bacteria synthesize and secrete small iron chelators termed siderophores. Siderophores have potent affinity for iron, which allows them to seize the essential metal from the host iron-binding proteins. To safeguard against iron thievery, the host relies upon the innate immune protein, lipocalin 2 (Lcn2), which could sequester catecholate-type siderophores and thus impede bacterial growth. However, certain bacteria are capable of outmaneuvering the host by either producing "stealth" siderophores or by expressing competitive antagonists that bind Lcn2 in lieu of siderophores. In this review, we summarize the mechanisms underlying the complex iron tug-of-war between host and bacteria with an emphasis on how host innate immunity responds to siderophores.

中文翻译：

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细菌铁载体和先天免疫之间的铁拔河。

铁是几乎所有需氧生物生存所必需的。在哺乳动物宿主中，铁是组装功能性铁硫 (Fe-S) 簇蛋白、血红素结合蛋白和调节各种功能（包括血红素合成、氧运输和 DNA 合成）的核糖核苷酸还原酶所需的辅助因子。然而，铁的生物利用度低，因为它在有氧条件下不溶。此外，宿主协调营养免疫反应以限制铁对潜在病原体的可及性。为了对抗营养免疫，大多数共生菌和致病菌合成并分泌称为铁载体的小铁螯合剂。铁载体对铁有很强的亲和力，这使它们能够从宿主铁结合蛋白中捕获必需的金属。为了防止偷铁，宿主依赖于先天免疫蛋白脂质运载蛋白 2 (Lcn2)，它可以隔离儿茶酚酸型铁载体，从而阻碍细菌生长。然而，某些细菌能够通过产生“隐形”铁载体或通过表达结合 Lcn2 代替铁载体的竞争性拮抗剂来战胜宿主。在这篇综述中，我们总结了宿主和细菌之间复杂的铁拉锯战的机制，重点是宿主先天免疫对铁载体的反应。铁载体或通过表达结合 Lcn2 的竞争性拮抗剂代替铁载体。在这篇综述中，我们总结了宿主和细菌之间复杂的铁拉锯战的机制，重点是宿主先天免疫对铁载体的反应。铁载体或通过表达结合 Lcn2 的竞争性拮抗剂代替铁载体。在这篇综述中，我们总结了宿主和细菌之间复杂的铁拉锯战的机制，重点是宿主先天免疫对铁载体的反应。