Name: bacillus anthracis infection pathways
Uploaded: 2026-05-20T13:52:42.329Z
Duration: 1 min 25 s
Channel: JoVE

Anthrax is caused by Bacillus anthracis spores that can enter the host through the skin, inhalation, or ingestion.In inhalation anthrax, spores reach the lungs. Alveolar macrophages phagocytose these spores and transport them to the lymph nodes.The spores germinate into vegetative bacteria, which kill the macrophages as they exit.These bacteria carry two plasmids that encode distinct virulence factors.pXO2 encodes a poly-D-glutamic acid capsule that inhibits phagocytosis.pXO1 encodes the anthrax exotoxin, which is made of three proteins: Protective Antigen PA, Edema Factor EF, and Lethal Factor LF.PA binds to host receptors and mediates endocytosis of EF and LF.Inside the endosome, PA forms a pore to translocate EF and LF into the host cytoplasm.EF causes tissue edema, while LF triggers cell death.As the infection advances, EF and LF enter the bloodstream, causing vascular leakage and systemic shock, which can lead to multiple organ failure.

inhalation anthrax

Inhalation Anthrax

Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive, spore-forming bacterium. It primarily affects herbivorous animals but can be transmitted to humans through skin contact, ingestion, or inhalation of spores.Cutaneous anthrax, the most common form, typically results from direct contact with bacterial spores through skin abrasions and is generally less severe. Gastrointestinal anthrax results from eating undercooked or contaminated meat. It affects the mouth, throat, or intestines and causes symptoms like nausea, vomiting, abdominal pain, and severe diarrhea. Inhalational anthrax, the most severe form, begins when aerosolized spores are inhaled and deposited in the alveolar spaces of the lungs. Alveolar macrophages then internalize the spores through phagocytosis and transport them to regional lymph nodes. There, the spores germinate into vegetative bacilli&#x2014;likely after macrophage lysis or in response to a nutrient-rich environment. Injection anthrax is a rare form seen in people who inject contaminated drugs. It resembles cutaneous anthrax but spreads faster, is harder to diagnose, and often involves deeper tissue damage.Two plasmids, pXO1 and pXO2, mediate the pathogenesis of B. anthracis. The pXO2 plasmid encodes a poly-D-glutamic acid capsule that protects the bacteria from phagocytic destruction by host immune cells. This antiphagocytic capsule is a critical virulence factor, enabling the bacteria to evade host defenses and disseminate within the host.The pXO1 plasmid encodes a tripartite exotoxin composed of Protective Antigen (PA), Edema Factor (EF), and Lethal Factor (LF). PA initiates toxin entry by binding to specific host cell receptors and mediating endocytosis of EF and LF. Within the acidified endosome, PA oligomerizes into a heptameric or octameric pore on the endosomal membrane to translocate EF and LF into the cytoplasm.Edema Factor is a calmodulin-dependent adenylate cyclase that increases intracellular cyclic AMP (cAMP) levels, disrupting cellular ion balance and leading to fluid accumulation and tissue edema. Lethal Factor is a zinc-dependent metalloprotease that cleaves mitogen-activated protein kinase kinases (MAPKKs), interrupting key signal transduction pathways and resulting in apoptosis of immune and endothelial cells.As the infection progresses, vegetative bacilli proliferate and release EF and LF into the bloodstream, contributing to systemic intoxication and tissue damage. This leads to widespread vascular leakage, impaired immune response, and eventually, systemic shock and multi-organ failure&#x2014;underscoring the lethality of inhalational anthrax if untreated.Due to its high lethality and ease of aerosolization, inhalational anthrax is a major concern in bioterrorism scenarios.

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bacillus anthracis infection pathways

Bacillus anthracis is a Gram-positive, spore-forming bacterium that causes anthrax. It is a zoonotic disease, which means it can spread from animals to humans. Herbivorous animals are the main hosts, but people can become infected through skin contact, eating contaminated meat, or breathing in spores.

Cutaneous anthrax is the most common form. It usually starts when spores enter through small skin breaks, and it is generally less severe. Gastrointestinal anthrax comes from eating undercooked or contaminated meat. It can affect the mouth, throat, or intestines, and it may cause nausea, vomiting, abdominal pain, and severe diarrhea.

Inhalational anthrax is the most severe form. It begins when aerosolized spores are inhaled and reach the alveolar spaces in the lungs. Alveolar macrophages, which are immune cells that engulf particles, take up the spores by phagocytosis and carry them to nearby lymph nodes. There, the spores may germinate into vegetative bacilli after macrophage lysis or in response to a nutrient-rich environment.

Injection anthrax is a rare form seen in people who inject contaminated drugs. It can look like cutaneous anthrax, but it spreads faster and is harder to diagnose. It also often causes deeper tissue damage.

Two plasmids, pXO1 and pXO2, control the disease process of B. anthracis. The pXO2 plasmid codes for a poly-D-glutamic acid capsule. This capsule helps the bacteria resist phagocytic destruction by host immune cells. It is a major virulence factor because it helps the bacteria evade defense cells and spread through the body.

The pXO1 plasmid codes for a tripartite exotoxin made of Protective Antigen, Edema Factor, and Lethal Factor. Protective Antigen binds to host cell receptors and helps bring Edema Factor and Lethal Factor into the cell by endocytosis. In the acidified endosome, Protective Antigen forms a heptameric or octameric pore in the membrane so the other toxin parts can move into the cytoplasm.

Bacillus Anthracis Infection Pathways

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Bacillus anthracis is a Gram-positive, spore-forming bacterium that causes anthrax. It is a zoonotic disease, which means it can spread from animals to humans. Herbivorous animals are the main hosts, but people can become infected through skin contact, eating contaminated meat, or breathing in spores. Cutaneous anthrax is the most common form. It usually starts when spores enter through small skin breaks, and it is generally less severe. Gastrointestinal anthrax comes from eating undercooked...

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key terms and concepts

Explore how Bacillus anthracis infects humans through skin, food, or inhaled spores, and learn how its capsule and toxins drive anthrax disease.

Bacillus Anthracis Infection Pathways | JoVE K12

JoVE Core Microbiology provides an engaging introduction to the microbial world and its influence on health, industry, and the environment. This comprehensive collection covers key concepts such as microbial structure, metabolism, genetics, and ecology. It introduces essential laboratory techniques and microscopy methods through visually engaging animations. Corresponding scientist-in-action videos bridge classroom concepts with real-world research and applications.

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Bacillus Anthracis Infection Pathways

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