Bacillus
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 Bacillus subtilis, Gram stained
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Bacillus anthracis |
Bacillus is a genus of rod-shaped, Gram-positive bacteria and a member of the division Firmicutes. Bacillus species are either obligate or facultative aerobes, and test positive for the enzyme catalase.[1] Ubiquitous in nature, Bacillus includes both free-living and pathogenic species. Under stressful environmental conditions, the cells produce oval endospores that can stay dormant for extended periods. These characteristics originally defined the genus, but not all such species are closely related, and many have been moved to other genera.[2]
Two Bacillus species are considered medically significant: B. anthracis, which causes anthrax, and B. cereus, which causes a foodborne illness similar to that of Staphylococcus.[3] A third species, B. thuringiensis, is an important insect pathogen, and is sometimes used to control insect pests. The type species is B. subtilis, an important model organism. It is also a notable food spoiler, as is B. coagulans.
An easy way to isolate Bacillus is by placing non-sterile soil in a test tube with water, shaking, placing in melted Mannitol Salt Agar, and incubating at room temperature for at least a day. Colonies are usually large, spreading and irregularly-shaped. Under the microscope, the Bacillus appear as rods, and a substantial portion usually contain an oval endospore at one end, making it bulge.
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[edit] The Cell Wall
The cell wall of Bacillus is a rigid structure on the outside of the cell that forms the first barrier between the bacterium and the environment, and at the same time maintains cell shape and withstands the pressure generated by the cell's turgor. The cell wall is composed of peptidoglycan, teichoic and teichuronic acids. B. subtilis is the first bacterium for which the role of an actin-like cytoskeleton in cell shape determination and peptidoglycan synthesis was identified and for which the entire set of peptidoglycan synthesizing enzymes was localised. The role of the cytoskeleton in shape generation and maintenance is important [4].
[edit] Word ambiguity
Although Bacillus, capitalized and italicized, specifically refers to the genus, the word bacillus may also be used to describe any rod-shaped bacterium, and in this sense, bacilli are found in many different taxonomic groups of bacteria.
Likewise, Bacilli refers to the particular class Bacillus belongs to, while bacilli are any rod-shaped bacteria.
It should be noted that the cell morphology term bacillus does not necessarily indicate gram-positive staining, as E. Coli is a gram negative rod-shaped bacteria.
[edit] See also
- Paenibacillus, a genus of bacteria that was formerly included in Bacillus
[edit] References
- ^ Turnbull PCB (1996). Bacillus. In: Barron's Medical Microbiology (Barron S et al, eds.), 4th ed., Univ of Texas Medical Branch. (via NCBI Bookshelf) ISBN 0-9631172-1-1.
- ^ Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.
- ^ Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9.
- ^ Scheffers DJ (2007). "The Cell Wall of Bacillus subtilis", Bacillus: Cellular and Molecular Biology (Graumann P, ed.). Caister Academic Press. ISBN 978-1-904455-12-7 .
