bacille

Bacillus is a term used in microbiology to describe a rod-shaped bacterium. In general language, a bacillus (plural bacilli) refers to any cylindrical, rod-like bacterium. In taxonomic practice, capitalized Bacillus denotes a genus of Gram-positive, rod-shaped bacteria that typically form endospores.

Many Bacillus species are aerobic or facultatively anaerobic and are widely found in soil, water, dust, and the gastrointestinal tracts of animals. They range from harmless soil inhabitants to important workhorses in industry, and some are notable pathogens. A key feature of many members of this genus is endospore formation, which allows survival under harsh environmental conditions and contributes to resistance to heat and desiccation.

Notable species include Bacillus anthracis (anthrax), Bacillus cereus (foodborne illness), Bacillus subtilis (a model organism in science and used for enzyme production), and Bacillus thuringiensis (used as a biological pesticide). Other Bacillus species are exploited to manufacture enzymes, antibiotics, and various biotechnological products.

Taxonomically, Bacillus belongs to the phylum Firmicutes, class Bacilli, order Bacillales, family Bacillaceae. The term bacillus also serves as a general descriptor for any rod-shaped bacterium, and the historical term bacille appears in names such as Bacille Calmette-Guérin (BCG) vaccine, based on Mycobacterium bovis.