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Methods

AFM imaging and analysis OMVs produced from different E. coli MG1655 strains were adsorbed onto freshly cleaved mica for 15min in DPBS buffer at room temperature. After adsorption, the sample was gently washed with fresh DPBS buffer for five times to remove non-adsorbed OMVs. Then OMVs were imaged using force-distance curve-based AFM (FD-based AFM) performed with an AFM (Nanoscope Multimode 8, Bruker) operated in PeakForce Tapping mode in buffer solution (DPBS) at room temperature. The AFM was equipped with a 120μm piezoelectric scanner and fluid cell. The images were recorded using two different AFM cantilevers: PEAKFORCE‐HiRs‐F‐A (Bruker) with a nominal spring constant of 0.4 N/m, a resonance frequency of≈ 165 kHz in liquid, and a sharpened silicon tip with a nominal radius of≈ 1 nm or SCANASYSTFLUID+(Bruker) with a nominal spring constant of 0.7 N/m, a …