What disease is caused by the bacterium Bacillus anthracis?

Bacillus anthracis causes the disease anthrax.

This Gram-positive, rod-shaped bacterium normally survives in soil as a tough endospore. Grazing animals can ingest the spores, and people may become infected through contact with infected animals or animal products, inhalation, ingestion, or contaminated wounds. Anthrax is therefore a zoonosis, meaning it can pass between animals and humans.

Human anthrax has several forms. Cutaneous anthrax is the most common and produces a typically painless sore that develops a characteristic black center, or eschar. Inhalation anthrax is much rarer but especially severe, while gastrointestinal anthrax follows ingestion of spores or contaminated meat. The bacterium’s capsule helps it evade immune cells, and its plasmids encode the components of anthrax toxin.

Robert Koch demonstrated in 1876 that B. anthracis caused anthrax, providing one of the earliest decisive experimental proofs of germ theory. The name anthracis comes from the Greek word for coal, referring to the dark skin lesion associated with the disease. Anthrax is unrelated to the skin condition sometimes called a carbuncle.