Anthrax Home > Bacillus Anthracis

The hardiness and toxicity of Bacillus anthracis make it a possible bioterrorism agent. This bacterium causes anthrax, and most commonly infects wild and domestic animals (cattle, sheep, goats, and other plant-eating animals). Infection can occur in humans when they are exposed to infected animals, tissue from infected animals, or when anthrax spores are used as a bioterrorist weapon.

What Is Bacillus Anthracis?

Bacillus anthracis is the bacterium that causes anthrax. This organism is different from many other bacteria because it forms spores. In this form, it can lie dormant (asleep), but may come to life with the right conditions. Once the bacteria come to life, they can have deadly effects.

Bacillus Anthracis Spores

Bacillus anthracis is an aerobic (oxygen-requiring) bacterium that lives in soil and has developed a survival tactic that allows it to endure for decades under the harshest conditions. As mentioned, this form is called a spore. You can think of a spore as a protective cocoon with the active bacterium inside.
When Bacillus anthracis is in its spore phase, it can withstand extreme heat, cold, and drought and continue to survive without nutrients or air. When environmental conditions are favorable, the spores will germinate into thriving colonies of bacteria. For example, a grazing animal may ingest spores that begin to grow, spread, and eventually kill the animal. The bacteria will form spores in the carcass and then return to the soil to infect other animals in the future.

Bacillus Anthracis Toxin

While the spore form of Bacillus anthracis allows it to survive in any environment, the ability to produce toxins is what makes it such a potent killer. Together, the hardiness and toxicity make this bacterium a formidable bioterrorism agent. Its toxin is made of three proteins:
  • Protective antigen
  • Edema factor
  • Lethal factor.
Protective Antigen
Protective antigen binds to select cells of an infected person or animal, and forms a channel that permits edema factor and lethal factor to enter those cells.
Written by/reviewed by:
Last reviewed by: Arthur Schoenstadt, MD
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