Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, B15 2TT, UK.
Quadram Institute Bioscience, Norwich Research Park, Norwich, NR4 7UA, UK.
Mol Microbiol. 2019 Feb;111(2):534-551. doi: 10.1111/mmi.14172. Epub 2018 Dec 18.
Enteroaggregative Escherichia coli (EAEC), is a diarrhoeagenic human pathogen commonly isolated from patients in both developing and industrialized countries. Pathogenic EAEC strains possess many virulence determinants, which are thought to be involved in causing disease, though, the exact mechanism by which EAEC causes diarrhoea is unclear. Typical EAEC strains possess the transcriptional regulator, AggR, which controls the expression of many virulence determinants, including the attachment adherence fimbriae (AAF) that are necessary for adherence to human gut epithelial cells. Here, using RNA-sequencing, we have investigated the AggR regulon from EAEC strain 042 and show that AggR regulates the transcription of genes on both the bacterial chromosome and the large virulence plasmid, pAA2. Due to the importance of fimbriae, we focused on the two AAF/II fimbrial gene clusters in EAEC 042 (afaB-aafCB and aafDA) and identified the promoter elements and AggR-binding sites required for fimbrial expression. In addition, we examined the organization of the fimbrial operon promoters from other important EAEC strains to understand the rules of AggR-dependent activation. Finally, we generated a series of semi-synthetic promoters to define the minimal sequence required for AggR-mediated activation and show that the correct positioning of a single AggR-binding site is sufficient to confer AggR-dependence.
肠聚集性大肠杆菌（EAEC）是一种从发展中国家和工业化国家的患者中分离出来的致腹泻性人类病原体。致病性 EAEC 菌株具有许多毒力决定因素，这些因素被认为与引起疾病有关，但 EAEC 引起腹泻的确切机制尚不清楚。典型的 EAEC 菌株具有转录调节因子 AggR，它控制许多毒力决定因素的表达，包括附着粘附菌毛（AAF），这对于附着到人类肠道上皮细胞是必需的。在这里，我们使用 RNA 测序研究了 EAEC 菌株 042 的 AggR 调控子，并表明 AggR 调节细菌染色体和大型毒力质粒 pAA2 上基因的转录。由于菌毛的重要性，我们专注于 EAEC 042 中的两个 AAF/II 菌毛基因簇（afaB-aafCB 和 aafDA），并确定了菌毛表达所需的启动子元件和 AggR 结合位点。此外，我们检查了其他重要 EAEC 菌株中菌毛操纵子启动子的组织，以了解 AggR 依赖性激活的规则。最后，我们生成了一系列半合成启动子，以定义 AggR 介导的激活所需的最小序列，并表明单个 AggR 结合位点的正确定位足以赋予 AggR 依赖性。
