The species can be obligate aerobes or facultative anaerobes,
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.