Iron restriction in mammals, part of innate antimicrobial defense, may be sensed as a signal by an infecting pathogen. Iron-dependent regulators not only activate the pathogen’s specific iron acquisition and storage mechanisms needed for survival but also influence a number of other processes. Bacterial extracellular vesicles (EVs) are a conserved communication mechanism, which can have roles in host colonization, transfer of antimicrobial resistance, modulation of the host’s immune response, and biofilm formation. Here we analyze the iron-responsive effect of RNA cargo from Escherichia coli EVs in bladder cells. No differences were found in total RNA quantified from EVs released from representative pathogenic and probiotic strains grown in different iron conditions; nevertheless, lipopolysaccharide (LPS) associated with purified RNA was 10 times greater from EVs derived from the pathogenic strain. The pathogen and probiotic EV-RNA have no substantial toxic effect on the viability of cultured bladder cells, regardless of the iron concentration during bacterial culture. Transcriptomic analysis of bladder cells treated with pathogen EV-RNA delivered in artificial liposomes revealed a gene expression profile with a strong similarity to that of cells treated with liposomes containing LPS alone, with the majority being immune response pathways. EV-RNA from the probiotic strain gave no significant perturbation of gene expression in bladder cells. Cytokine profiling showed that EV-LPS has a role modulating the immune response when internalized by bladder cells, highlighting a key factor that must be considered when evaluating functional studies of bacterial RNA.

哺乳动物中的铁限制是​​先天抗微生物防御的一部分，可被感染的病原体感知为信号。依赖铁的调节剂不仅激活了病原体生存所需的特定铁获取和存储机制，而且还影响许多其他过程。细菌细胞外囊泡（EVs）是一种保守的通讯机制，可以在宿主定植，抗菌素耐药性转移，宿主免疫应答调节和生物膜形成中发挥作用。在这里，我们分析了来自大肠杆菌膀胱细胞中的电动汽车。从在不同铁条件下生长的代表性致病菌和益生菌菌株释放的电动汽车定量的总RNA中未发现差异；然而，与纯化的RNA相关的脂多糖（LPS）较致病株衍生的EV大10倍。无论细菌培养过程中的铁浓度如何，病原体和益生菌EV-RNA对培养的膀胱细胞的活力均没有实质性的毒性作用。对在人工脂质体中用病原体EV-RNA处理的膀胱细胞进行的转录组学分析显示，该基因表达谱与仅含LPS的脂质体处理的细胞具有高度相似性，其中大多数是免疫应答途径。益生菌菌株的EV-RNA对膀胱细胞中的基因表达无明显干扰。细胞因子分析表明，EV-LPS在被膀胱细胞内化后具有调节免疫反应的作用，突显了评估细菌RNA功能研究时必须考虑的关键因素。