To overcome the metal restriction imposed by the host’s nutritional immunity, pathogenic bacteria use high metal affinity molecules called metallophores. Metallophore‐mediated metal uptake pathways necessitate complex cycles of synthesis, secretion, and recovery of the metallophore across the bacterial envelope. We recently discovered staphylopine and pseudopaline, two members of a new family of broad‐spectrum metallophores important for bacterial survival during infections. Here, we are expending the molecular understanding of the pseudopaline transport cycle across the diderm envelope of the Gram‐negative bacterium Pseudomonas aeruginosa. We first explored pseudopaline secretion by performing in vivo quantifications in various genetic backgrounds and revealed the specific involvement of the MexAB–OprM efflux pump in pseudopaline transport across the outer membrane. We then addressed the recovery part of the cycle by investigating the fate of the recaptured metal‐loaded pseudopaline. To do so, we combined in vitro reconstitution experiments and in vivo phenotyping in absence of pseudopaline transporters to reveal the existence of a pseudopaline modification mechanism, possibly involved in the metal release following pseudopaline recovery. Overall, our data allowed us to provide an improved molecular model of secretion, recovery, and fate of this important metallophore by P. aeruginosa.

中文翻译：

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铜绿假单胞菌 MexAB – OprM 外排泵参与金属细胞假色斑的分泌

为了克服宿主营养免疫所施加的金属限制，病原菌使用称为金属团的高金属亲和力分子。金属团介导的金属摄取途径需要金属团跨细菌包膜的合成、分泌和回收的复杂循环。我们最近发现了 staphylopine 和 pseudopaline，这是广谱金属载体新家族的两个成员，对感染期间的细菌存活很重要。在这里，我们正在扩展对跨革兰氏阴性细菌铜绿假单胞菌的双皮层包膜的假苍白运输循环的分子理解. 我们首先通过在各种遗传背景下进行体内定量研究了假性肠粉的分泌，并揭示了 MexAB – OprM 外排泵在假性肠粉质跨外膜转运中的具体参与。然后，我们通过调查重新捕获的载有金属的拟苍色的命运来解决循环的恢复部分。为此，我们结合了体外重建实验和体内表型分析，在没有假paline 转运蛋白的情况下揭示了假paline 修饰机制的存在，这可能与假paline 恢复后的金属释放有关。总体而言，我们的数据使我们能够提供一种改进的分子模型，用于了解铜绿假单胞菌这一重要金属团的分泌、恢复和命运。