Differences in bacillus & clostridium

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Differences in bacillus & clostridium
Identifiable by their long rod-like shape, clostridium bacteria take on many forms, from botulism to tetanus. (Duncan Smith/Photodisc/Getty Images)

Encompassing two genera of bacteria that remain highly dangerous to humans, bacilli and clostridia make up an exclusive subset of spore-forming, rod-shaped bacteria. Best known as anthrax (Bacillus anthracis) and tetanus (Clostridium tetani), these bacteria can be separated by their need for oxygen. Both bacteria remain important tools in the study and treatment of disease.

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Characterised as opportunistic pathogens that produce disease in humans through the release of exotoxins, clostridia subsist all around us: in soil, sewage and human and animal intestines. Clostridia are similar in appearance to bacilli because of their rod-like shape, and both bacteria feature thick cell walls making them Gram-positive. The formation of spores also sets these two bacteria apart from other genera. However, clostridia differ from bacilli in that the latter is anaerobic -- clostridia do not require oxygen for survival.

Diseases and Uses of Clostridium

In humans, clostridium species produce a variety of life-threatening diseases: gas gangrene, tetanus and botulism. However, botulinum toxin, better known as "botox," has been harvested from Clostridium botulinum for its desirous muscle relaxing effects for the face, which can reduce the appearance of wrinkles. Most clostridium species also engage in fermentation to produce the organic solvent butanol, which is used in the commercial solvent industries.


Like clostridia, bacilli are rod-shaped, spore-producing, Gram-positive bacteria, but these bacteria differ in that bacilli require oxygen -- they are aerobes. Further, unlike clostridia, bacilli thrive in diverse environments throughout the world, in extreme hot and cold and even acidic environments, and have a reputation for extreme environmental tolerance. Unlike clostridia, only two of the known 48 species of bacilli affect humans.

Diseases and Uses of Bacillus

Bacillus anthracis has become well-known for its abilities to produce the highly fatal anthrax spore, while Bacillus cereus goes rather unnoticed, but is responsible for food poisoning. Anthrax must be treated with penicillin quickly to avoid death and is the only known bacteria with its own protein capsule. The other bacillus species have no negative effects on humans, and many are used to synthesise enzymes in the detergent and pharmaceutical manufacturing industries.


Vaccines for the prevention of Clostridium tetani have been available and required for decades, while Clostridium botulinum can be fought with antitoxins. Neither measure has proven effective against Clostridium perfringens, the bacterium that causes gas gangrene. Bacillus anthracis can be prevented with an avirulent spore vaccine, and penicillin is often prescribed in cases of all of these infections with varying measures of success.

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