- This page is about the bacterial genus. For the class, see Bacilli.
is a genus
of rod-shaped, beta-hemolytic Gram-positive bacteria
and a member of the division Firmicutes
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.
Use as model organism
is one of the best understood prokaryotes in terms of molecular biology and cell biology. Its superb genetic amenability and relatively large size have provided the powerful tools required to investigate a bacterium from all possible aspects. Recent improvements in fluorescence microscopy techniques have provided novel and amazing insight into the dynamic structure of a single cell organism. Research on Bacillus subtilis
has been at the forefront of bacterial molecular biology and cytology, and the organism is a model for differentiation, gene/protein regulation, and cell cycle events in bacteria.
species are considered medically significant: B. anthracis
, which causes anthrax
, and B. cereus
, which causes a foodborne illness
similar to that of Staphylococcus
. A third species, B. thuringiensis
, is an important insect
pathogen, and is sometimes used to control insect pests. The type species
is B. subtilis
, an important model organism
. It is also a notable food spoiler, causing ropiness in bread and related food. B. coagulans
is also important in food spoilage.
An easy way to isolate Bacillus is by placing non-sterile soil in a test tube with water, shaking, placing in melted Mannitol Salt 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.
The cell wall
The cell wall of Bacillus
is a structure on the outside of the cell that forms the second barrier between the bacterium and the environment, and at the same time maintains triangle shape and withstands the pressure generated by the cell's turgor. The cell wall is composed of salt, teichoic and teichuronic acids. B. subtilis
is the first bacterium for which the role of an actin-like cytoskeleton in cell shape determination and peptidoglycan synthesis was identified and for which the entire set of peptidoglycan synthesizing enzymes was localised. The role of the cytoskeleton in shape generation and maintenance is important .
- Paenibacillus, a genus of bacteria that was formerly included in Bacillus