Bacillus (plural bacilli) describes bacteria that have a cylindrical or rod-like shape. (Other bacterial shapes are coccus and spirillum.) Bacilli can be either aerobic (living in the presence of and needing oxygen) and anaerobic (living without oxygen). Common bacilli include those that cause anthrax (Bacillus anthracis) in humans and farm animals such as cattle, swine and sheep, as well as rabbits, mice and guinea pigs.
Bacillus globigii, Bacillus subtilis, grass bacillus, or hay bacillus are found in soil and decomposing organic matter. Some strains produce antibiotics.
Eubacteria, eubacterium, true bacteria are a large group of bacteria with rigid cell walls. Those with flagella (active tails) are motile.
Genus Bacillaceae includes many saprophytes important in decay of organic matter and a number of parasites.