Human_Salmonella_secreting_outer_membrane_vesicles_in_vivo_in_chicken_ileum_%28Original_work_of_Dr_R_C_YashRoy%29

Bacterial outer membrane vesicles (OMVs) are

vesicles Vesicle may refer to: ; In cellular biology or chemistry * Vesicle (biology and chemistry), a supramolecular assembly of lipid molecules, like a cell membrane * Synaptic vesicle ; In human embryology * Vesicle (embryology), bulge-like features o ...

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

released from the outer membranes of

Gram-negative bacteria Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wall ...

. These vesicles were the first bacterial membrane vesicles (MVs) to be discovered, while Gram-positive bacteria release vesicles as well. Outer membrane vesicles were first discovered and characterized using transmission-electron microscopy by

Indian Indian or Indians may refer to: Peoples South Asia * Indian people, people of Indian nationality, or people who have an Indian ancestor ** Non-resident Indian, a citizen of India who has temporarily emigrated to another country * South Asia ...

Scientist Prof. Smriti Narayan Chatterjee and J. Das in 1966-67. OMVs are ascribed the functionality to provide a manner to communicate among themselves, with other

microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

s in their environment and with the host. These vesicles are involved in

trafficking Smuggling is the illegal transportation of objects, substances, information or people, such as out of a house or buildings, into a prison, or across an international border, in violation of applicable laws or other regulations. There are various ...

bacterial

cell signaling In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellula ...

biochemicals, which may include DNA, RNA, proteins,

endotoxins Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer me ...

and allied

virulence Virulence is a pathogen's or microorganism's ability to cause damage to a host. In most, especially in animal systems, virulence refers to the degree of damage caused by a microbe to its host. The pathogenicity of an organism—its ability to ...

molecules. This communication happens in

microbial culture A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagn ...

s in oceans, inside animals, plants and even inside the human body. Gram-negative bacteria deploy their

periplasm The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found that ...

to secrete OMVs for trafficking bacterial biochemicals to target cells in their environment. OMVs also carry endotoxic

lipopolysaccharide Lipopolysaccharides (LPS) are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins. They are composed of an O-antigen, an outer core, and an inner core all joined by a covalent bond, and are found in the outer ...

initiating disease process in their host. This mechanism imparts a variety of benefits like, long-distance delivery of bacterial secretory cargo with minimized hydrolytic degradation and extra-cellular dilution, also supplemented with other supportive molecules (e.g., virulence factors) to accomplish a specific job and yet, keeping a safe-distance from the defense arsenal of the targeted cells. Biochemical signals trafficked by OMVs may vary largely during 'war and peace' situations. In 'complacent' bacterial colonies, OMVs may be used to carry DNA to 'related' microbes for genetic transformations, and also translocate

molecules for

quorum sensing In biology, quorum sensing or quorum signalling (QS) is the ability to detect and respond to cell population density by gene regulation. As one example, QS enables bacteria to restrict the expression of specific genes to the high cell densities at ...

and

biofilm A biofilm comprises any syntrophic consortium of microorganisms in which cells stick to each other and often also to a surface. These adherent cells become embedded within a slimy extracellular matrix that is composed of extracellular ...

formation. During 'challenge' from other cell types around, OMVs may be preferred to carry degradation and subversion enzymes. Likewise, OMVs may contain more of invasion proteins at the host-pathogen interface (Fig. 1). It is expected, that environmental factors around the secretory microbes are responsible for inducing these bacteria to synthesize and secrete specifically-enriched OMVs, physiologically suiting the immediate task. Thus, bacterial OMVs, being strong

immunomodulators Immunotherapy or biological therapy is the treatment of disease by activating or suppressing the immune system. Immunotherapies designed to elicit or amplify an immune response are classified as ''activation immunotherapies,'' while immunotherap ...

, can be manipulated for their

immunogenic Immunogenicity is the ability of a foreign substance, such as an antigen, to provoke an immune response in the body of a human or other animal. It may be wanted or unwanted: * Wanted immunogenicity typically relates to vaccines, where the injectio ...

contents and utilized as potent

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

-free

vaccines A vaccine is a biological preparation that provides active acquired immunity to a particular infectious or malignant disease. The safety and effectiveness of vaccines has been widely studied and verified.< ...

for immunizing humans and animals against threatening

infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dis ...

Biogenesis and movement

Gram-negative bacteria have a double set of bilayers. An inner bilayer, the inner

cell membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment ( ...

, encloses the

cytoplasm In cell biology, the cytoplasm is all of the material within a eukaryotic cell, enclosed by the cell membrane, except for the cell nucleus. The material inside the nucleus and contained within the nuclear membrane is termed the nucleoplasm. ...

cytosol The cytosol, also known as cytoplasmic matrix or groundplasm, is one of the liquids found inside cells ( intracellular fluid (ICF)). It is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondri ...

. Surrounding this inner cell membrane there is a second bilayer called the

bacterial outer membrane The bacterial outer membrane is found in gram-negative bacteria. Its composition is distinct from that of the inner cytoplasmic cell membrane - among other things, the outer leaflet of the outer membrane of many gram-negative bacteria includes ...

. The compartment or space between these two membranes is called the

periplasmic space The periplasm is a concentrated gel-like matrix in the space between the inner cytoplasmic membrane and the bacterial outer membrane called the ''periplasmic space'' in gram-negative bacteria. Using cryo-electron microscopy it has been found tha ...

. In addition, there is a firm cell wall consisting of

peptidoglycan Peptidoglycan or murein is a unique large macromolecule, a polysaccharide, consisting of sugars and amino acids that forms a mesh-like peptidoglycan layer outside the plasma membrane, the rigid cell wall (murein sacculus) characteristic of most ba ...

layer, which surrounds the cell membrane and occupies the periplasmic space. The peptidoglycan layer provides some rigidity for maintaining the bacterial cell shape, besides also protecting the microbe against challenging environments. The first step in

biogenesis Spontaneous generation is a superseded scientific theory that held that living creatures could arise from nonliving matter and that such processes were commonplace and regular. It was hypothesized that certain forms, such as fleas, could arise ...

of gram-negative bacterial OMVs, is ''bulging'' of outer membrane above the peptidoglycan layer. Accumulation of phospholipids in the outside of the outer membrane is thought to be the basis of this outwards bulging of the outer membrane. This accumulation of phospholipids can be regulated by the VacJ/Yrb ABC transport system that transfers phospholipids from the outside of OM to the inner side. Additionally, environmental conditions as sulfur depletion can trigger a state of phospholipid overproduction that causes increased OMV release. The actual release of the vesicle from the outer membrane remains unclear. It is likely that vesicle structures can be released spontaneously. Alternatively, it has been suggested that few proteins 'rivet' the outer and cell membranes together, so that the periplasmic bulge protrudes like a 'ballooned' pocket of inflated periplasm out from the surface of the outer membrane. Lateral diffusion of 'rivet complexes' may help in pinching off large bulges of periplasm as OMVs.YashRoy R C (2003) Eucaryotic cell intoxication by Gram-negative organisms: A novel bacterial outermembrane-bound nanovesicular model for Type-III secretion system. ''Toxicology International'', vol. 10 (No. 1), 1-9.https://www.academia.edu/7695646/YashRoy_R_C_2003_Eukaryotic_cell_intoxication_by_Gram-negative_pathogens_A_novel_bacterial_outer_membrane-bound_nanovesicular_exocytosis_model_for_Type-III_secretion_system._Toxicology_International._Vol._10_No._1_pp._1-9 Bacterial membrane vesicles dispersion along the cell surface was measured in live ''

Escherichia coli ''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus '' Esc ...

'', commensal bacteria common in the human gut. Antibiotic treatment altered vesicle dynamics, vesicle-to-membrane affinity, and surface properties of the cell membranes, generally enhancing vesicle transport along the surfaces of bacterial membranes and suggesting that their motion properties could be a signature of antibiotic stress. Despite this first high-resolution, quantitative tracking of bacterial OMVs, detailed experimental work is still awaited to understand the

biomechanics Biomechanics is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. Biomechanics is a branch of ...

of OMV biogenesis and transport. OMVs are also under focus of current research in exocytosis in prokaryotes via outer

membrane vesicle trafficking Membrane vesicle trafficking in eukaryotic animal cells involves movement of biochemical signal molecules from synthesis-and-packaging locations in the Golgi body to specific release locations on the inside of the plasma membrane of the secretory ...

for intra-species, inter-species and inter-kingdom

, which is slated to change our mindset on

of microbes, host-pathogen interactions and inter-relationships among variety of species in earth's

ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...

References

{{reflist Membrane biology Bacteriology

Biogenesis and movement

See also

References