Bacterial Membrane Vesicles: Physiological Roles, Infection Immunology, and Applications

Abstract

Bacterial or fungal membrane vesicles, traditionally considered as microbial metabolic wastes, are secreted mainly from the outer membrane or cell membrane of microorganisms. However, recent studies have shown that these vesicles play essential roles in direct or indirect communications among microorganisms and between microorganisms and hosts. This review aims to provide an updated understanding of the physiological functions and emerging applications of bacterial membrane vesicles, with a focus on their biogenesis, mechanisms of adsorption and invasion into host cells, immune stimulatory effects, and roles in the much‐concerned problem of bacterial resistance. Additionally, the potential applications of these vesicles as biomarkers, vaccine candidates, and drug delivery platforms are discussed.

Plant exosome nanovesicles (PENs): green delivery platforms

“…Exosomes have a spherical structure consisting of a phospholipid bilayer that allows them to embed or adsorb various drugs between the bilayers and encapsulate different types of drugs within the internal cavity. 78,[101][102][103][104] These vesicles can be used as nano-delivery vehicles for the targeted delivery of anticancer drugs due to their natural biosafety, low immunogenicity, potential cancer cell targeting, and enhanced cellular uptake through direct fusion with the plasma membrane. To accomplish this objective, it is necessary to artificially load the desired drug into the exosome, which requires drug delivery from the exosome.…”

“…Inflammatory bowel diseases (IBDs) are chronic autoimmune diseases that affect the gastrointestinal tract, including ulcerative colitis and Crohn's disease. [76][77][78][79][80] Symptoms can include intermittent relapses and remissions of inflammation, with environmental or genetic factors, intestinal microbiota, and immune response playing a role in pathogenesis. 11 When ingested orally, phytoexosome-like vesicles maintain their stable structure in the stomach's acidic environment and reach the small intestine via a vesicular transport mechanism.…”

Bacterial membrane vesicles in the pathogenesis and treatment of inflammatory bowel disease

“… 4 , 22 Blebbing of the outer membrane in Gram-negative bacteria is reported to occur as a result of a disturbance in the cell envelope due to intercalating of the hydrophobic molecules into the outer membrane or from the unbalanced biosynthesis of the cell membrane. 4 , 22 Three mechanisms that involve membrane blebbing have been described and these include the reduced cross‐linking between the outer membrane and the underlying peptidoglycan, 38 , 39 the accumulation of peptidoglycan fragments or misfolded proteins in the periplasmic space, 39 and vesicles derived from bacterium flagellar-sheaths upon rotation of the flagella. 39 …”

“… 4 , 22 Three mechanisms that involve membrane blebbing have been described and these include the reduced cross‐linking between the outer membrane and the underlying peptidoglycan, 38 , 39 the accumulation of peptidoglycan fragments or misfolded proteins in the periplasmic space, 39 and vesicles derived from bacterium flagellar-sheaths upon rotation of the flagella. 39 …”

“…aeruginosa . 39 , 44 , 45 Mutants of Porphyromonas gingivalis deficient in autolysin demonstrated an increase in MVs production, and this emanated from the inability of the bacterium to breakdown periplasmic peptidoglycan fragments that accumulated in the periplasm due to the lack of autolysins in P . gingivalis .…”