The rise of antibiotic resistance is a growing worldwide human health issue, with major socioeconomic implications. An understanding of the interactions occurring at the bacterial membrane is crucial for the generation of new antibiotics. Supported lipid bilayers (SLBs) made from reconstituted lipid vesicles have been used to mimic these membranes, but their utility has been restricted by the simplistic nature of these systems. A breakthrough in the field has come with the use of outer membrane vesicles derived from Gram-negative bacteria to form SLBs, thus providing a more physiologically relevant system. These complex bilayer systems hold promise but have not yet been fully characterized in terms of their composition, ratio of natural to synthetic components, and membrane protein content. Here, we use correlative atomic force microscopy (AFM) with structured illumination microscopy (SIM) for the accurate mapping of complex lipid bilayers that consist of a synthetic fraction and a fraction of lipids derived from Escherichia coli outer membrane vesicles (OMVs). We exploit the high resolution and molecular specificity that SIM can offer to identify areas of interest in these bilayers and the enhanced resolution that AFM provides to create detailed topography maps of the bilayers. We are thus able to understand the way in which the two different lipid fractions (natural and synthetic) mix within the bilayers, and we can quantify the amount of bacterial membrane incorporated into the bilayer. We prove the system’s tunability by generating bilayers made using OMVs engineered to contain a green fluorescent protein (GFP) binding nanobody fused with the porin OmpA. We are able to directly visualize protein–protein interactions between GFP and the nanobody complex. Our work sets the foundation for accurately understanding the composition and properties of OMV-derived SLBs to generate a high-resolution platform for investigating bacterial membrane interactions for the development of next-generation antibiotics.

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相关显微镜揭示可调谐细菌外膜模型的纳米级特征

抗生素耐药性的上升是一个日益严重的全球人类健康问题，具有重大的社会经济影响。了解细菌膜上发生的相互作用对于新抗生素的产生至关重要。由重组脂质囊泡制成的支持脂质双层 (SLB) 已被用于模拟这些膜，但它们的实用性受到这些系统的简单性质的限制。该领域的一项突破是使用源自革兰氏阴性菌的外膜囊泡形成 SLB，从而提供了一个更具生理相关性的系统。这些复杂的双层系统具有前景，但在其组成、天然成分与合成成分的比例以及膜蛋白含量方面尚未完全表征。这里，大肠杆菌外膜囊泡（OMV）。我们利用 SIM 可以提供的高分辨率和分子特异性来识别这些双层中感兴趣的区域，以及 AFM 提供的增强分辨率来创建双层的详细地形图。因此，我们能够了解两种不同的脂质部分（天然和合成）在双层中混合的方式，并且我们可以量化掺入双层中的细菌膜的量。我们通过生成使用 OMV 制成的双层来证明系统的可调性，这些 OMV 被设计为包含与孔蛋白 OmpA 融合的绿色荧光蛋白 (GFP) 结合纳米体。我们能够直接可视化 GFP 和纳米抗体复合物之间的蛋白质-蛋白质相互作用。