Bacillus anthracis
A Microbial Biorealm page on the genus Bacillus anthracis
Classification
Higher order taxa
cellular organisms; Bacteria (domain); Firmicutes (phylum); Bacilli (class); Bacillales (order); Bacillaceae (family); Bacillus (genus); Bacillus cereus group
Genus
Bacillus anthracis
NCBI: Taxonomy |
Description and significance
Describe the appearance, habitat, etc. of the organism, and why it is important enough to have its genome sequenced. Describe how and where it was isolated. Include a picture or two (with sources) if you can find them.
Genome structure
Describe the size and content of the genome. How many chromosomes? Circular or linear? Other interesting features? What is known about its sequence? Does it have any plasmids? Are they important to the organism's lifestyle?
Cell structure and metabolism
Describe any interesting features and/or cell structures; how it gains energy; what important molecules it produces.
Ecology
Describe any interactions with other organisms (included eukaryotes), contributions to the environment, effect on environment, etc.
Pathology
Bacillus anthracis causes the anthrax diesease, which represents a complex interaction between the host and parasite. The organism penetrates into the blood stream and harms the host by producing toxins within the body. The toxin is a complex of three plasmid-encoded proteins. Two of the proteins are directly toxic, including LF (lethal factor) and EF (edema factor). LF destroys white blood cells while EF increases cyclic AMP levels. Energy and water balance is impaired by the increase in cyclic AMP. The other plasmid-encoded protein, named PA (protective antigen), ushers the two toxic proteins in cells. PA forms a multimeric ring, which inserts into the cell membranes of the host. PA is not toxic alone, but if it is inactivated, the two toxic proteins would not cause harm. This is because PA allows the toxic components to pass through the membrane via a special toxin delivery system. The slimy capsule layer that surrounds Bacillus anthracis allows it to resist phagocytosis by white cells.
There are two common disease forms: cutaneous and pulmonary. The cutaneous form is caused by handling contaminated materials, and the pulmonary form is caused by inhalation. Skin abrasions allow spores to enter and cause local lesions by germinating there. Patients with a cutaneous anthrax diesease mostly recover within 10 days, although a few progress to a life-threatening disease. The pulmonary form of the disease results in a higher mortlity rate because the organism spreads through circulation. Macrophages in the lung's alveoli take up the spores and permit entry into the body.
Until the 20th century, anthrax was a prevalent diesease in humans and cattle. It is still an important pathogen in some countries today. Some scholars believe that the Egyptian plagues in the Bible may have been caused by Anthrax. However, most people had not heard of anthrax until the recent 2001 scare in the United States. Robert Koch and Louis Pasteur developed a vaccine against anthrax, which was the first infectious disease they studied. The vaccines today are not fully effective. However, if the disease is diagnosed soon enough after infection, treatment is effective. Methods to detect the organism quickly and new vaccines are under development. Because Bacillus anthracis lives in many soils, outbreaks are still reported. In fact, in the upper Midwest of the United States, many farms are under quarantine due to anthrax.
During the 20th century anthrax was used as a weapon in many countries. it has also been directed toward farm animals for warfare. The significance of anthrax as a terror weapon was realized in 2001. Although small outbreaks can result in a strong response, some people argue that anthrax is not an ideal biological weapon because the organism is not particularly pathogenic. To infect people, a large number of spores are needed. Also, anthrax is almost never transmitted between people. The most effective form of anthrax is a very fine powder. Therefore, to make anthrax a weapon, the preparation needs to be grinded into a fine powder. Anticaking agents are necessary as well to prevent clumping of the spores. Bacillus anthracis can be engineered to be resistant to antibiotics even though they are usually sensitive to antibiotics including penicillin and ciprofloxacin.
How does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
Application to Biotechnology
Does this organism produce any useful compounds or enzymes? What are they and how are they used?
Current Research
Enter summaries of the most recent research here--at least three required
References
example:
Wheeler DL, Chappey C, Lash AE, Leipe DD, Madden TL, Schuler GD, Tatusova TA, Rapp BA (2000). Database resources of the National Center for Biotechnology Information. Nucleic Acids Res 2000 Jan 1;28(1):10-4 [PubMed]
Edited by Grace Ucar, student of Rachel Larsen and Kit Pogliano