Outer Membrane Vesicles

Abstract

Outer membrane vesicles (blebs) are produced by Escherichia coli, Salmonella, and all other gram-negative bacteria both in vitro and in vivo. Most of the research in the field has focused on the properties of vesicles derived from pathogenic bacteria and their interactions with eukaryotic cells. These data indicate that vesicles are able to contribute to pathogenesis. Thus, it appears that pathogenic gram-negative bacteria have co-opted vesicles for the dissemination of virulence determinants. However, the role of vesicle production by nonpathogenic bacteria is less obvious. This section reviews the data demonstrating the mechanistic and physiological basis of outer membrane vesicle production by bacteria. Vesiculation can be seen as a mechanism for cells to react to conditions in the surrounding environment by carrying away unnecessary components and allowing rapid modification of the outer membrane composition. In addition, vesicles can transmit biological activities distant from the originating cell. Vesicles could act to bind and deplete host immune factors at the site of infection that would otherwise attack the bacteria. Vesicles in the area surrounding the cell may also provide the cell protection inside a human or animal host. The concept of vesicles as virulence factors has received considerable attention, and they are likely to play a significant role in the pathogenesis of gram-negative bacteria. By analysis of their composition, mechanism of formation, regulation, and physiological function, progress is being made in understanding the ubiquitous nature of outer membrane vesicles produced by gram-negative bacteria.

Bacterial outer membrane vesicles and the host–pathogen interaction

“…Naturally produced bacterial vesicles are discrete, closed OM blebs produced by growing cells, not products of cell lysis or cell death (Mug-Opstelten and Witholt 1978;Zhou et al 1998;Yaganza et al 2004;McBroom and Kuehn 2005). By electron microscopy, vesicles appear spherical with a bilayer membrane, electron-dense luminal content, and an average diameter of 50-250 nm, depending on the strain (Beveridge 1999).…”

Significances of OMV and Extracellular Vesicle Proteomics

“…Native OMVs contain only lipids and protein of the outer membrane as well as periplasm but do not contain components of cytoplasm and inner membrane. This was confirmed from density gradient-purified OMV analysis [62]. To understand the mechanism of vesicle formation and release, deletion of yfgL gene, leads to remarkable decline in formation and release of OMV and in an adherent-invasive strain of E. coli K12 and E. coli (AIEC) [65].…”

“…Prokaryotes, eukaryotes (archaea [40,41], Gram-negative and Gram-positive bacteria [42][43][44][45], fungi [45][46] and parasites [50,51] produce the spherical, membranous vesicles from the outer cell surface. Archaeal membrane vesicles (diameter 90-230 nm) contain Slayer proteins and membrane lipids, which has been obtained from the surface of archaeal cell [41,52].…”

“…The ubiquitous process of vesiculation helps in the survival of Gram-negative bacteria in different conditions of environments [3]. Naturally produced membrane vesicles are very distinct, closed blebs of outer membrane released by budding cells, rather due to cell lysis or death [14,[62][63][64]. The utmost rate of membrane vesicle formation takes place at the end of log phase and is plentiful at the sites of cell division, as explained for B. melitensis, E. coli and Vibrio cholera [8,[20][21][22][23][24].…”

“…Various vesiculation mechanism theories based on genetic and biochemical data have been studied [62]. The ubiquitous process of vesiculation helps in the survival of Gram-negative bacteria in different conditions of environments [3].…”