Enterohemorrhagic Escherichia coli (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.

中文翻译：

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质膜脂质成分对肠出血性大肠杆菌鞭毛介导的粘附的影响。

肠出血性大肠杆菌(EHEC) O157:H7 是食源性胃肠道疾病的主要原因。EHEC 与宿主组织的粘附是实现细菌定植的第一步。菌毛和鞭毛等粘附素介导这一过程。在这里，我们使用巨型单层囊泡（GUV）作为生物学相关模型研究了细菌鞭毛与宿主细胞质膜的相互作用。培养的细胞系含有许多不同的分子成分，包括蛋白质和糖蛋白。相比之下，利用 GUV，我们可以表征细菌仅与细胞膜的特定脂质部分相互作用的模式。GUV 上的细菌粘附取决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，我们发现脂质堆积是实现细菌粘附的关键参数。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-亚麻酸降低了野生型 EHEC 的粘附，但不会降低无鞭毛突变体的粘附。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可防止鞭毛粘附在膜双层上，并对最佳宿主定植发挥明显作用。鞭毛介导的质膜粘附对宿主与病原体的相互作用具有广泛的影响。