Clostridium botulinum

Clostridium botulinum is a gram-positive, rod-shaped, anaerobic, spore-forming, motile bacterium with no flagella and has the ability to produce botulinum toxin, which is a neurotoxin.

C. botulinum is a diverse group of pathogenic bacteria. Initially, they were grouped together by their ability to produce botulinum toxin and are now known as four distinct groups, C. botulinum groups I–IV. Along with some strains of Clostridium butyricum and Clostridium baratii, these bacteria all produce the toxin.

Botulinum toxin can cause botulism, a severe flaccid paralytic disease in humans and other animals. The botulinum toxin is the most potent toxin known in scientific literature, natural or synthetic, with a lethal dose of 1.3–2.1 ng/kg in humans.

C. botulinum is commonly associated with bulging canned food; bulging, misshapen cans can be due to an internal increase in pressure caused by gas produced by bacteria.

C. botulinum is responsible for foodborne botulism (ingestion of preformed toxin), infant botulism (intestinal infection with toxin-forming C. botulinum), and wound botulism (infection of a wound with C. botulinum). C. botulinum produces heat-resistant endospores that are commonly found in soil and are able to survive under adverse conditions.

C. botulinum is a Gram-positive, rod-shaped, spore-forming bacterium. It is an obligate anaerobe, requiring an environment that lacks oxygen. However, C. botulinum tolerates traces of oxygen due to the enzyme superoxide dismutase, which is an important antioxidant defense in nearly all cells exposed to oxygen. C. botulinum is able to produce the neurotoxin only during sporulation, which can happen only in an anaerobic environment.

C. botulinum is divided into four distinct phenotypic groups (I-IV) and is also classified into seven serotypes (A–G) based on the antigenicity of the botulinum toxin produced. On the level visible to DNA sequences, the phenotypic grouping matches the results of whole-genome and rRNA analyses, and setotype grouping approximates the result of analyses focused specifically on the toxin sequence. The two phylogenetic trees do not match because of the ability of the toxin gene cluster to be horizontally transferred.

Botulinum neurotoxin (BoNT) production is the unifying feature of the species. Seven serotypes of toxins have been identified that are allocated a letter (A–G), several of which can cause disease in humans. They are resistant to degradation by enzymes found in the gastrointestinal tract. This allows for ingested toxins to be absorbed from the intestines into the bloodstream. Toxins can be further differentiated into subtypes on the bases of smaller variations. However, all types of botulinum toxin are rapidly destroyed by heating to 100 °C for 15 minutes (900 seconds). 80 °C for 30 minutes also destroys BoNT.