FIGURE 1.

Biogenesis and types of BEVs. Gram‐negative BEVs have two main pathways of formation, namely, blebbing and explosive cell lysis. Blebbing results in the formation of OMV and OIMV, respectively. When the curvature of the membrane changes due to various reasons, the outer membrane protrudes and then falls off, forming OMV. Therefore, OMV contains outer membrane proteins and periplasmic contents but does not include substances from the inner membrane and cytoplasm. On the other hand, OIMV is another blebbing mechanism where the inner membrane protrudes into the periplasm after the weakening of PG layer by autolysins, followed by detachment along with the outer membrane. Therefore, OIMV can contain substances from both the inner membrane and cytoplasm. Explosive cell lysis is triggered by endolysins causing cell protrusion and explosion to form EOMVs. In addition, self‐assembly of the inner membrane with cytoplasmic contents can lead to irregular vesicles within the outer membrane which then form EOIMV. Gram‐positive bacteria also have two pathways for vesicle formation: Blebbing caused by loosening of PG layer allows small vesicles formed by cytoplasmic membrane protrusions to pass through thick PG layers to form CMVs; additionally, endolysins also can induce bubbling cell death resulting in ECMVs which differ from CMVs. BEVs, bacteria extracellular vesicles; CMVs, cytoplasmic membrane‐derived vesicles; ECMVs, explosive cytoplasmic membrane vesicles; EOIMV, explosive outer‐inner membrane vesicle; EOMVs, explosive outer membrane vesicles; OIMV, outer‐inner membrane vesicle; OMV, outer membrane vesicles; PG, peptidoglycan.