Bacillus anthracis
Each cell is about 1 by 6
μms in size.
B. anthracis was the first bacterium conclusively demonstrated to cause disease, by
Robert Koch in 1877.
The species name
anthracis is from the
Greek anthrakis (ἄνθραξ), meaning
coal and referring to the most common form of the disease, cutaneous anthrax, in which large black skin
lesions are formed.
Under conditions of environmental stress,
B. anthracis bacteria naturally produce endospores which rest in the soil and can survive for decades in this state. When ingested by a cattle, sheep, or other
herbivores, the bacteria begin to reproduce inside the animal and eventually kill it, then continue to reproduce in its carcass. Once the nutrients are exhausted, new endospores are produced and the cycle repeats.
has as least 89 known
strains, ranging from highly virulent strains with
biological warfare and
bioterrorism applications (
Ames and
Vollum) to benign strains used for
inoculations (
Sterne). The strains differ in presence and activity of various
genes, determining their
virulence and production of
antigens and
toxins. The form associated with the
2001 anthrax attacks contains a
toxin consisting of three
proteins:
the protective antigen, the edema factor and the lethal factor.
Infections with
B. anthracis can be treated with
β-lactam antibiotics such as
penicillin, and others which are active against Gram-positive bacteria.
