FIGURE 1.

Extracellular vesicles produced by bacteria and archaea. (A) Gram-negative eubacteria release outer membrane vesicles (OMVs) by budding. A similar process results in the formation of outer-inner membrane vesicles (O-IMVs), with remodeling of the cell wall. Cell lysis induced by phage or environmental stress can also release O-IMVs and explosive OMVs (E-OMVs). It is unknown if similar processes occur in the small number of diderm archaeal species. (B) In gram-positive eubacteria and monoderm Euryarcheota, cytoplasmic membrane vesicles (CMVs) are released via cell membrane budding and cell wall re-modeling or as the result of cell lysis where the vesicles are extruded through gaps in the rigid cell wall. In the Crenarcheaota, CMVs are released via the action of the archaeal ESCRT machinery. See also Table 1.