Bacillus

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iBacillus

Bacillus subtilis, Gram stained

Scientific classification

Kingdom:	Bacteria
Division:	Firmicutes
Class:	Bacilli
Order:	Bacillales
Family:	Bacillaceae
Genus:	Bacillus Cohn 1872

Species

Bacillus anthracis
Bacillus cereus
Bacillus coagulans
Bacillus natto
Bacillus subtilis
Bacillus thuringiensis
etc.

This page is about the bacterial genus Bacillus. The word bacillus may also be used to describe any rod-shaped bacterium, and in this sense, bacilli are found in many different groups of bacteria. When the particular genus Bacillus is referred to, it is capitalized and italicized. 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.

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.<ref name=Barron>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.</ref> 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.<ref name=Brock>Madigan M; Martinko J (editors). (2005). Brock Biology of Microorganisms, 11th ed., Prentice Hall. ISBN 0-13-144329-1.</ref>

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.<ref name=Sherris>Ryan KJ; Ray CG (editors) (2004). Sherris Medical Microbiology, 4th ed., McGraw Hill. ISBN 0-8385-8529-9.</ref> 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.