Wednesday, July 05, 2006

Bacillus

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.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.

An easy way to isolate Bacillus is by placing non-sterile soil in a test tube with water, shaking, placing in melted mannitol salts 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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