FIGURE 1: A conserved ABC transport system and its relevance for OMV biogenesis in Gram-negative bacteria. (A) Illustration of the VacJ/Yrb ABC transport system in H. influenzae that putatively prevents PL accumulation in the outer leaflet of the OM by retrograde trafficking of PLs from the OM to the inner membrane (IM). The model is based on findings in E. coli published by Malinverni and Silhavy. (B) A new model of OMV formation in Gram-negative bacteria. Step 1: Decreased expression or deletion of vacJ and/or yrb genes results in PL accumulation in the outer leaflet of the OM. This asymmetric expansion of the outer leaflet initiates an outward bulging of the OM. Step 2: Further enrichment of positive and negative curvature-inducing PLs in both leaflets supports the budding of the OM, which finally pinches off to form an OMV. Step 3: The released OMV is enriched in PLs incorporated into the outer leaflet of the vesicle membrane. Copyright disclaimer notice: the figure is composed of Figure 1a and Figure 8 of the original article (Roier et. al, doi:10.1038/ncomms10515), which is licensed under a Creative Commons Attribution 4.0 International License.