Clostridium botulinum

          

           Clostridium botulinum is a rod-shaped microorganism. It is an obligate anaerobe, meaning that oxygen is poisonous to the cells. However, C. botulinum tolerates traces of oxygen due to the enzyme called superoxide dismutase (SOD) which is an important antioxidant defense in nearly all cells exposed to oxygen.C. botulinum is only able to produce the neurotoxin during sporulation, which can only happen in an anaerobic environment. Other bacterial species produce spores in an unfavorable growth environment to preserve the organism's viability and permit survival in a dormant state until the spores are exposed to favorable conditions.

             In the laboratory Clostridium botulinum is usually isolated in tryptose sulfite cycloserine (TSC) growth media in an anaerobic environment with less than 2% of oxygen. This can be achieved by several commercial kits that use a chemical reaction to replace O₂ with CO₂ (E.J. GasPak System). C. botulinum is a lipase negative microorganism that grows between pH of 4.8 and 7 and it can't use lactose as a primary carbon source, characteristics important during a biochemical identification.

           Clostridium botulinum was first recognized and isolated in 1895 by Emile van Ermengem from home cured ham implicated in a botulism outbreak. The isolate was originally named Bacillus botulinus. However, isolates from subsequent outbreaks were always found to be anaerobic spore formers, so Bengston proposed that the organism be placed into the genus Clostridium as the Bacillus genus was restricted to aerobic spore-forming rods.

             Since 1959 all species producing the botulinum neurotoxins (types A-G) have been designated C. botulinum. Substantial phenotypic and genotypic evidence exists to demonstrate heterogeneity within the species. This has led to the reclassification of C. botulinum type G strains as a new species Clostridium argentinense.

             Clostridium botulinum strains that do not produce a botulin toxin are referred to as Clostridium sporogenes. The complete genome of C. botulinum has been sequenced Sanger.