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Related Concept Videos

Overview of Secretory Vesicles01:33

Overview of Secretory Vesicles

Secretory vesicles, also known as dense core vesicles (DCVs), are membrane-bound vesicles that transport secretory proteins, such as hormones or neurotransmitters. Regulated secretory vesicles transport proteins from the trans-Golgi network to the exterior of the cell. Proteins present in regulated secretory vesicles are required to be rapidly exocytosed in large amounts upon a specific stimulus.
Various proteins regulate the aggregation of molecules inside the secretory vesicles. Chromogranins...
Surface Membrane Barriers01:18

Surface Membrane Barriers

The skin and mucous membranes serve as the primary line of defense against pathogens by providing both physical and chemical protection. These barriers are essential in preventing the entry and establishment of microbes, thereby maintaining the integrity of the host.
The outer layer of the skin, the epidermis, is a robust barrier comprising layers of closely packed keratinized cells. This dense arrangement prevents microbes from penetrating the body. The periodic shedding of epidermal cells...
Defense Against Bacterial Pathogens01:31

Defense Against Bacterial Pathogens

The human immune system is a complex network of cells, tissues, and organs that work together to defend the body against bacterial infections. It consists of various immune cells, each playing a specific role in the defense mechanism.
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
Fusion of Secretory Vesicles with the Plasma Membrane01:26

Fusion of Secretory Vesicles with the Plasma Membrane

Proteins and neurotransmitters in secretory vesicles can be released from a cell upon vesicle docking, priming, and fusion with the plasma membrane. Vesicles are docked and primed in preparation for the quick exocytosis of their contents in response to a stimulus. The fusion process is mainly carried out by a SNAP Receptor or SNARE complex, consisting of synaptobrevin, syntaxin-1, and SNAP-25.
In 1993, Jim Rothman proposed that the antiparallel pairing of vesicular and transmembrane SNAREs, or...
Defense Mechanism Against Infection01:26

Defense Mechanism Against Infection

Natural flora, body system defenses, and inflammation are natural barriers of the body against infectious agents regardless of previous exposure. Normal floras of the human body refer to the microbial population that colonizes the skin and mucous membranes.
In addition, many body organ systems have unique defenses against infection. The skin is an intact, multilayered surface preventing invasion by microorganisms unless impaired. Mucous membranes lining the mouth, nose, and eyelids are barriers...
Bacterial Toxins01:12

Bacterial Toxins

Bacterial toxins are sophisticated virulence factors that enable pathogenic bacteria to interact with, invade, and damage host tissues. These toxins fall broadly into two types: protein exotoxins, which are secreted into the environment and target specific host receptors, and lipopolysaccharide endotoxins, which are structural components of the bacterial outer membrane released primarily during bacterial lysis or membrane shedding. Exotoxins generally act more selectively, binding to cell...

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Extracellular Vesicles and Bacteriophages: New Directions in Environmental Biocolloid Research.

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Related Experiment Video

Updated: May 17, 2026

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
08:34

Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

Published on: February 22, 2017

Secreted bacterial vesicles as good samaritans.

Meta J Kuehn

    Cell Host & Microbe
    |October 23, 2012
    PubMed
    Summary

    Bacteroides fragilis produces polysaccharide A (PSA), a molecule that promotes immune tolerance in the gut. Researchers discovered that PSA is unexpectedly packaged within outer membrane vesicles (OMVs) secreted by the bacteria.

    Area of Science:

    • Microbiology
    • Immunology
    • Gastroenterology

    Background:

    • Commensal bacteria like Bacteroides fragilis play a crucial role in maintaining gut homeostasis.
    • Immune tolerance in the gastrointestinal tract is essential for preventing inflammatory responses to food antigens and commensal microbes.
    • Polysaccharide A (PSA) is a key molecule produced by B. fragilis implicated in immune modulation.

    Discussion:

    • The study by Shen et al. (2012) investigated the natural secretion of PSA.
    • Contrary to expectations, PSA was found to be encapsulated within outer membrane vesicles (OMVs).
    • Outer membrane vesicles are bacterial-derived structures with diverse biological functions.

    Key Insights:

    • Bacteroides fragilis utilizes outer membrane vesicles (OMVs) as a vehicle for delivering polysaccharide A (PSA).

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    Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages
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    Legionella pneumophila Outer Membrane Vesicles: Isolation and Analysis of Their Pro-inflammatory Potential on Macrophages

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    Enrichment of Native and Recombinant Extracellular Vesicles of Mycobacteria

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    Size Exclusion Chromatography to Analyze Bacterial Outer Membrane Vesicle Heterogeneity

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  • This packaging mechanism suggests a novel route for PSA's interaction with the host immune system.
  • The discovery challenges previous assumptions about PSA secretion and delivery.

    • Outlook:

    • Further research is needed to elucidate the precise mechanisms of OMV-mediated PSA transport and immune interaction.
    • Understanding this pathway could reveal new therapeutic strategies for inflammatory and autoimmune diseases.
    • Investigating OMVs from other commensal bacteria may uncover similar immune-modulating delivery systems.