Bacillus

(plural bacilli)

a BACTERIUM which has a rod-shaped form.

Taken from Dictionary of Science
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Bacillus is a genus of rod-shaped bacteria and a member of the division Firmicutes. Bacillus species are obligate 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.

Taken from Wikipedia