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Updated: Jun 7, 2026
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Recombinant Protein Expression, Crystallization, and Biophysical Studies of a Bacillus-conserved Nucleotide Pyrophosphorylase, BcMazG
Published on: May 16, 2017
Bacillus anthracis produces membrane-derived vesicles containing biologically active toxins
Johanna Rivera1, Radames J B Cordero, Antonio S Nakouzi
1Department of Microbiology and Immunology, Division of Infectious Diseases, The Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Summary
Bacillus anthracis secretes toxins via extracellular vesicles, enhancing potency and offering new vaccine targets. These vesicles deliver toxins to host cells, and immunization with them improves survival in mice.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Gram-positive bacteria
Background:
- Extracellular vesicle (EV) production is common in Gram-negative bacteria, but poorly understood in Gram-positive species.
- Bacillus anthracis, a Gram-positive bacterium and biowarfare agent, produces EVs.
- These EVs are double-membraned spheres (50-150 nm) originating from the bacterial outer layer.
Purpose of the Study:
- To investigate the role of extracellular vesicles in Bacillus anthracis toxin secretion.
- To characterize the composition and function of B. anthracis EVs.
- To assess the immunogenicity and protective potential of B. anthracis EVs.
Main Methods:
- Isolation and characterization of extracellular vesicles from B. anthracis.
- Immunoelectron microscopy using monoclonal antibodies (mAbs) against key toxins (protective antigen, lethal factor, edema toxin) and anthrolysin.
- ELISA and immunoblot analysis to confirm toxin presence in vesicles.
- Macrophage infection assays with different B. anthracis strains and vesicle preparations.
- Immunization of BALB/c mice with vesicles followed by B. anthracis challenge.
Main Results:
- B. anthracis EVs contain toxin components (protective antigen, lethal factor, edema toxin) and anthrolysin.
- Some EVs contained multiple toxin components, and toxin-containing EVs were found within infected macrophages.
- Monoclonal antibody targeting protective antigen demonstrated vesicle-mediated delivery of toxins.
- Vesicles were immunogenic in mice, eliciting an IgM response to toxin components.
- Mice immunized with vesicles showed significantly increased survival after B. anthracis challenge.
Conclusions:
- Extracellular vesicle secretion is a significant pathway for toxin delivery in Bacillus anthracis.
- Vesicle-associated toxin secretion concentrates toxins for enhanced potency against host cells.
- These findings have implications for developing vaccines and passive antibody strategies against B. anthracis.
- B. anthracis EVs provide a novel system for studying secretory pathways in Gram-positive bacteria.
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