AskDefine | Define bacillus

Dictionary Definition

Bacillus n : aerobic rod-shaped spore-producing bacterium; often occurring in chainlike formations; found primarily in soil [syn: Bacilli, B]

User Contributed Dictionary

see Bacillus



From bacillus "little staff, wand".


  1. Any of various rod-shaped, spore-forming aerobic bacteria in the genus Bacillus, some of which cause disease



Alternative spellings


Diminutive of baculus "staff, walking stick"


  1. A small staff or wand.
  2. The shaft or handle of a tool or weapon.

Extensive Definition

This page is about the bacterial genus. For the class, see Bacilli.
For rod-shaped bacteria in general, see Bacteria.
For the stick insect genus, see Bacillus (insect).
Bacillus is a genus of rod-shaped, beta-hemolytic Gram-positive bacteria and a member of the division Firmicutes. Bacillus 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.
Bacillus subtilis 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.
Two Bacillus 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 .

Word ambiguity

Although Bacillus, capitalized and italicized, specifically refers to the genus, the word 'bacillus' may also be used to describe any rod-shaped bacterium, and in this sense, bacilli are found in many different taxonomic groups of bacteria.
Likewise, Bacilli refers to the particular class Bacillus belongs to, while bacilli are any rod-shaped bacteria.
It should be noted that the cell morphology term bacillus does not necessarily indicate Gram-positive staining, as E. coli is a Gram-negative, rod-shaped bacteria.

See also

  • Paenibacillus, a genus of bacteria that was formerly included in Bacillus


bacillus in Czech: Bacillus
bacillus in German: Bazillus
bacillus in Spanish: Bacilo
bacillus in Esperanto: Bacilo
bacillus in Basque: Bacillus
bacillus in French: Bacillus
bacillus in Italian: Bacillus (batteri)
bacillus in Hebrew: Bacillus
bacillus in Japanese: バシラス属
bacillus in Norwegian: Basiller
bacillus in Polish: Laseczka
bacillus in Portuguese: Bacilo
bacillus in Russian: Бациллы
bacillus in Simple English: Bacillus
bacillus in Slovenian: Bacillus
bacillus in Swedish: Bacill
bacillus in Vietnamese: Trực khuẩn
bacillus in Turkish: Bacillus
bacillus in Ukrainian: Bacillus
bacillus in Yiddish: באצילן
bacillus in Chinese: 芽孢桿菌屬

Synonyms, Antonyms and Related Words

adenovirus, aerobe, aerobic bacteria, amoeba, anaerobe, anaerobic bacteria, bacteria, bacterium, bug, coccus, disease-producing microorganism, echovirus, enterovirus, filterable virus, fungus, germ, gram-negative bacteria, gram-positive bacteria, microbe, microorganism, mold, nonfilterable virus, pathogen, picornavirus, protozoa, protozoon, reovirus, rhinovirus, rickettsia, spirillum, spirochete, spore, staphylococcus, streptococcus, trypanosome, vibrio, virus
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