Mechanistic working models of OMV production and modulation. Models of how changes in envelope structure lead to modulation of OMV production are based on the data presented here and in prior studies, as described in the text. (A) Modulation of PG structure and metabolism can up- and downregulate OMV production through levels of bound Lpp (circled in red). (B) Periplasmic bulk accumulation (red aggregates) leads to hypervesiculation without altering bound Lpp levels. (C) The IM anchored lipoprotein NlpA contributes to envelope integrity in conjunction with Lpp and OmpA.