肠致病性大肠杆菌临床分离株中 III 型分泌系统活性的表型多样性。

Carmen A Contreras, Tracy H Hazen, Carmen Guadarrama, Ramón Cervantes-Rivera, Theresa J Ochoa, Pablo Vinuesa, David A Rasko, Jose L Puente
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引用次数: 0

摘要

导言。肠致病性大肠杆菌(EPEC)菌株是发展中国家儿童严重腹泻的主要病因,对儿童构成了严重威胁。EPEC 的致病性依赖于由肠道细胞损伤基因座(LEE)编码的 III 型分泌系统(T3SS),该系统可促进细菌效应蛋白的分泌和转运。虽然在 EPEC 原型菌株 E2348/69 中,PerC(质粒编码的调节因子)和 GrlA(LEE 激活因子的全局调节因子)在 ler 表达和 LEE 基因激活中的调控作用已得到充分证实,但了解临床 EPEC 分离株之间 LEE 基因表达调控机制的变异性仍是一个需要进一步研究的领域。本研究旨在通过比较分析在有利于PerC或GrlA介导的LEE表达激活的特定生长条件下的分泌谱,探索临床EPEC分离株之间LEE基因表达控制机制的多样性。我们比较了典型 EPEC(tEPEC)和非典型 EPEC(aEPEC)临床分离株在有利于 PerC 或 GrlA 介导的激活 LEE 表达的生长条件下依赖 T3SS 的分泌模式和启动子表达。此外,我们还进行了启动子报告活性测定、定量实时 PCR 和 Western 印迹实验,以评估基因表达活性。在 tEPEC 和 aEPEC 菌株之间观察到了 T3SS 依赖性分泌的显著差异,这与 LEE 序列变异或 T3SS 基因的功能无关。值得注意的是,一种临床 tEPEC 分离物在抑制性生长条件下以及在 PerC 和 GrlA 均缺失的情况下表现出分泌水平升高,这表明 Ler(LEE 编码的调节因子)表达的激活存在另一种机制。我们的研究结果表明,未表征的 LEE 调控机制导致了临床 EPEC 分离物的表型多样性,但它们对临床结果的影响仍然未知。这对基于参考菌株的传统认识提出了挑战,并凸显了超越既有模型进行研究以全面阐明 EPEC 发病机制的必要性。
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Phenotypic diversity of type III secretion system activity in enteropathogenic Escherichia coli clinical isolates.

Introduction. Enteropathogenic Escherichia coli (EPEC) strains pose a significant threat as a leading cause of severe childhood diarrhoea in developing nations. EPEC pathogenicity relies on the type III secretion system (T3SS) encoded by the locus of enterocyte effacement (LEE), facilitating the secretion and translocation of bacterial effector proteins.Gap Statement. While the regulatory roles of PerC (plasmid-encoded regulator) and GrlA (global regulator of LEE-activator) in ler expression and LEE gene activation are well-documented in the EPEC prototype strain E2348/69, understanding the variability in LEE gene expression control mechanisms among clinical EPEC isolates remains an area requiring further investigation.Aim. This study aims to explore the diversity in LEE gene expression control mechanisms among clinical EPEC isolates through a comparative analysis of secretion profiles under defined growth conditions favouring either PerC- or GrlA-mediated activation of LEE expression.Methodology. We compared T3SS-dependent secretion patterns and promoter expression in both typical EPEC (tEPEC) and atypical EPEC (aEPEC) clinical isolates under growth conditions favouring either PerC- or GrlA-mediated activation of LEE expression. Additionally, we conducted promoter reporter activity assays, quantitative real-time PCR and Western blot experiments to assess gene expression activity.Results. Significant differences in T3SS-dependent secretion were observed among tEPEC and aEPEC strains, independent of LEE sequence variations or T3SS gene functionality. Notably, a clinical tEPEC isolate exhibited increased secretion levels under repressive growth conditions and in the absence of both PerC and GrlA, implicating an alternative mechanism in the activation of Ler (LEE-encoded regulator) expression.Conclusion. Our findings indicate that uncharacterized LEE regulatory mechanisms contribute to phenotypic diversity among clinical EPEC isolates, though their impact on clinical outcomes remains unknown. This challenges the conventional understanding based on reference strains and highlights the need to investigate beyond established models to comprehensively elucidate EPEC pathogenesis.

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