Université de Technologie de Compiègne, UPJV, UMR CNRS 7025, Enzyme and Cell Engineering, Centre de recherche Royallieu, Compiègne, France.
Institute for Biology-Bacterial Physiology, Humboldt-Universität zu Berlin, Berlin, Germany.
mSphere. 2020 Sep 16;5(5):e00702-20. doi: 10.1128/mSphere.00702-20.
Enterohemorrhagic (EHEC) O157:H7 is a major cause of foodborne gastrointestinal illness. The adhesion of EHEC to host tissues is the first step enabling bacterial colonization. Adhesins such as fimbriae and flagella mediate this process. Here, we studied the interaction of the bacterial flagellum with the host cell's plasma membrane using giant unilamellar vesicles (GUVs) as a biologically relevant model. Cultured cell lines contain many different molecular components, including proteins and glycoproteins. In contrast, with GUVs, we can characterize the bacterial mode of interaction solely with a defined lipid part of the cell membrane. Bacterial adhesion on GUVs was dependent on the presence of the flagellar filament and its motility. By testing different phospholipid head groups, the nature of the fatty acid chains, or the liposome curvature, we found that lipid packing is a key parameter to enable bacterial adhesion. Using HT-29 cells grown in the presence of polyunsaturated fatty acid (α-linolenic acid) or saturated fatty acid (palmitic acid), we found that α-linolenic acid reduced adhesion of wild-type EHEC but not of a nonflagellated mutant. Finally, our results reveal that the presence of flagella is advantageous for the bacteria to bind to lipid rafts. We speculate that polyunsaturated fatty acids prevent flagellar adhesion on membrane bilayers and play a clear role for optimal host colonization. Flagellum-mediated adhesion to plasma membranes has broad implications for host-pathogen interactions. Bacterial adhesion is a crucial step to allow bacteria to colonize their hosts, invade tissues, and form biofilm. Enterohemorrhagic O157:H7 is a human pathogen and the causative agent of diarrhea and hemorrhagic colitis. Here, we use biomimetic membrane models and cell lines to decipher the impact of lipid content of the plasma membrane on enterohemorrhagic flagellum-mediated adhesion. Our findings provide evidence that polyunsaturated fatty acid (α-linolenic acid) inhibits flagellar adhesion to the plasma membrane in a mechanism separate from its antimicrobial and anti-inflammatory functions. In addition, we confirm that cholesterol-enriched lipid microdomains, often called lipid rafts, are important in bacterial adhesion. These findings demonstrate that plasma membrane adhesion via bacterial flagella play a significant role for an important human pathogen. This mechanism represents a promising target for the development of novel antiadhesion therapies.
肠出血性（EHEC）O157：H7 是食源性胃肠道疾病的主要原因。EHEC 与宿主组织的黏附是细菌定植的第一步。菌毛和鞭毛等黏附素介导了这一过程。在这里，我们使用巨单层囊泡（GUV）作为生物相关模型研究了细菌鞭毛与宿主细胞膜的相互作用。培养的细胞系包含许多不同的分子成分，包括蛋白质和糖蛋白。相比之下，使用 GUV 可以仅用细胞膜的定义脂质部分来表征细菌的相互作用模式。细菌在 GUV 上的黏附依赖于鞭毛丝的存在及其运动性。通过测试不同的磷脂头基、脂肪酸链的性质或脂质体曲率，我们发现脂质包装是使细菌黏附的关键参数。使用在多不饱和脂肪酸（α-亚麻酸）或饱和脂肪酸（棕榈酸）存在下生长的 HT-29 细胞，我们发现 α-亚麻酸减少了野生型 EHEC 的黏附，但对无鞭毛突变体没有影响。最后，我们的结果表明，鞭毛的存在有利于细菌与脂筏结合。我们推测多不饱和脂肪酸阻止鞭毛在膜双层上的黏附，并在最佳宿主定植中发挥明显作用。通过质膜的鞭毛介导的黏附对宿主-病原体相互作用具有广泛的意义。细菌黏附是允许细菌定植宿主、侵袭组织和形成生物膜的关键步骤。肠出血性 O157：H7 是一种人类病原体，也是腹泻和出血性结肠炎的病原体。在这里，我们使用仿生膜模型和细胞系来解析质膜脂质含量对肠出血性鞭毛介导的黏附的影响。我们的研究结果提供了证据表明，多不饱和脂肪酸（α-亚麻酸）通过一种与抗微生物和抗炎功能分开的机制抑制了鞭毛与质膜的黏附。此外，我们证实富含胆固醇的脂质微区，通常称为脂筏，在细菌黏附中很重要。这些发现表明，通过细菌鞭毛与质膜的黏附在一种重要的人类病原体中起着重要作用。该机制代表了开发新型抗黏附疗法的有前途的目标。
