Myxobacteria with compatible TraA proteins engage in homotypic interactions that bring the cells into close approximation for outer-membrane fusion. OM lipids and proteins are freely exchanged between the cells, but TraA itself is not transferred due to interactions with TraB, which is tethered to the peptidoglycan (PG) cell wall. Polymorphic SitA effectors are among the many lipoproteins transferred during OME. SitA nucleases ultimately disengage from the OM and enter the cytoplasm through an uncharacterized mechanism. Abbreviations: IM, inner membrane; OM, outer membrane; PG, peptidoglycan.