PDF(Pubmed)
Abstract：
Urinary tract infection (UTI) is a ubiquitous infectious condition, and uropathogenic Escherichia coli (UPEC) is the predominant causative agent of UTI. Copper (Cu) is implicated in innate immunity, including against UPEC. Cu is a trace element utilized as a co-factor, but excess Cu is toxic due to mismetalation of non-cognate proteins. E. coli precisely regulates Cu homeostasis via efflux systems. However, Cu import mechanisms into the bacterial cell are not clear. We hypothesized that Cu import defective mutants would exhibit increased resistance to Cu. This hypothesis was tested in a forward genetic screen with transposon (Tn5) insertion mutants in UPEC strain CFT073, and we identified 32 unique Cu-resistant mutants. Transposon and defined mutants lacking yhiM, which encodes a hypothetical inner membrane protein, were more resistant to Cu than parental strain. Loss of YhiM led to decreased cellular Cu content and increased expression of copA, encoding a Cu efflux pump. The CpxAR envelope stress response system was activated in the ΔyhiM mutant as indicated by increased expression of cpxP. Transcription of yhiM was regulated by CueR and CpxR, and the CpxAR system was essential for increased Cu resistance in the ΔyhiM mutant. Importantly, activation of CpxAR system in the ΔyhiM mutant was independent of NlpE, a known activator of this system. YhiM was required for optimal fitness of UPEC in a mouse model of UTI. Our findings demonstrate that YhiM is a critical mediator of Cu homeostasis and links bacterial adaptation to Cu stress with the CpxAR-dependent envelope stress response in UPEC.IMPORTANCEUPEC is a common bacterial infection. Bacterial pathogens are exposed to host-derived Cu during infection, including UTI. Here, we describe detection of genes involved in Cu homeostasis in UPEC. A UPEC mutant lacking YhiM, a membrane protein, exhibited dramatic increase in resistance to Cu. Our study demonstrates YhiM as a nexus between Cu stress and the CpxAR-dependent envelope stress response system. Importantly, our findings establish NlpE-independent activation of CpxAR system during Cu stress in UPEC. Collectively, YhiM emerges as a critical mediator of Cu homeostasis in UPEC and highlights the interlinked nature of bacterial adaptation to survival during Cu and envelope stress.
摘要：
尿路感染（UTI）是一种普遍存在的感染性疾病，尿路致病性大肠杆菌（UPEC）是UTI的主要病原体。铜（Cu）与先天免疫有关，包括反对UPEC。Cu是一种用作辅因子的微量元素，但过量的铜由于非同源蛋白的误金属化而有毒。大肠杆菌通过外排系统精确调节Cu稳态。然而,Cu进入细菌细胞的机制尚不清楚。我们假设铜进口缺陷突变体会表现出对铜的抗性增加。在UPEC菌株CFT073中使用转座子（Tn5）插入突变体在正向遗传筛选中测试了该假设，我们鉴定了32个独特的铜抗性突变体。缺乏yhiM的转座子和确定的突变体，它编码一种假设的内膜蛋白，对Cu的抗性比亲本菌株更强。YhiM的缺失导致细胞Cu含量降低和copA表达增加,编码铜外排泵。CpxAR包膜应激反应系统在ΔyhiM突变体中被激活，如cpxP表达增加所示。yhiM的转录受CueR和CpxR调控,并且CpxAR系统对于ΔyhiM突变体中增加的Cu抗性至关重要。重要的是,ΔyhiM突变体中CpxAR系统的激活与NlpE无关，该系统的已知活化剂。YhiM对于UPEC在UTI小鼠模型中的最佳适合性是必需的。我们的发现表明，YhiM是Cu稳态的关键介质，并将细菌对Cu胁迫的适应与UPEC中CpxAR依赖的包膜应激反应联系起来。IMPORTANCEUPEC是一种常见的细菌感染。细菌病原体在感染过程中暴露于宿主来源的铜，包括UTI。这里,我们描述了在UPEC中检测与Cu稳态有关的基因。缺乏YhiM的UPEC突变体,一种膜蛋白，对Cu的抗性显着增加。我们的研究表明YhiM是Cu应力与CpxAR依赖的包络应力响应系统之间的联系。重要的是,我们的发现建立了在UPEC中Cu胁迫期间CpxAR系统的NlpE非依赖性激活。总的来说，YhiM成为UPEC中Cu稳态的关键介质，并强调了细菌在Cu和包膜胁迫期间对生存的适应的相互联系的性质。
