Clostridium

Clostridium is a genus of Gram-positive bacteria belonging to the Firmicutes. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped, which gives them their name, from the Greek kloster (κλωστήρ) or spindle. These characteristics traditionally defined the genus; but many species originally classified as Clostridium have been reclassified in other genera.

Overview

Clostridium contains around 100 species that include common free-living bacteria, as well as important pathogens. The five main species responsible for disease in humans are:

• C. botulinum can produce botulinum toxin in food or wounds and can cause botulism. Honey sometimes contains spores of C. botulinum, which may cause infant botulism in humans one year old and younger. The toxin eventually paralyzes the infant's breathing muscles. Adults and older children can eat honey safely, because Clostridium species do not compete well with the other rapidly growing bacteria present in the gastrointestinal tract. This same toxin is known as Botox and is used cosmetically to paralyze facial muscles to reduce the signs of aging; it also has numerous therapeutic uses.
• C. difficile can flourish when other bacteria in the gut are killed during antibiotic therapy, leading to pseudomembranous colitis (a cause of antibiotic-associated diarrhea).
• C. perfringens, formerly called C. welchii, causes a wide range of symptoms, from food poisoning to gas gangrene. It also causes enterotoxemia (also known as "overeating disease" or "pulpy kidney disease") in sheep and goats. C. perfringens also takes the place of yeast in the making of salt rising bread. The name perfringens means 'breaking through' or 'breaking in pieces'.
• C. tetani is the causative organism of tetanus. The name is derived from Ancient Greek: τέτανος tetanos "taut", and τείνειν teinein "to stretch", due to the violent spasms caused by C. tetani infection.
• C. sordellii can cause a fatal infection in exceptionally rare cases after medical abortions. Fewer than one case per year has been reported since 2000.

C. sordellii is sometimes found in raw swiftlet nests, a Chinese delicacy. Nests are washed in a sulfite solution to kill the bacteria before being exported to the U.S.

Neurotoxin production is the unifying feature of the species C. botulinum. Eight types of toxins have been identified and allocated a letter (A-H). Most strains produce one type of neurotoxin, but strains producing multiple toxins have been described. C. botulinum producing B and F toxin types have been isolated from human botulism cases in New Mexico and California. The toxin type has been designated Bf as the type B toxin was found in excess of the type F. Similarly, strains producing Ab and Af toxins have been reported.

Organisms genetically identified as other Clostridium species have caused human botulism: Clostridium butyricum producing type E toxin and Clostridium baratii producing type F toxin. The ability of C. botulinum to naturally transfer neurotoxin genes to other Clostridium species is concerning, especially in the food industry where preservation systems are designed to destroy or inhibit only C. botulinum, but not other Clostridium species.

Commercial uses

C. thermocellum can use lignocellulosic waste and generate ethanol, thus making it a possible candidate for use in production of ethanol fuel. It also has no oxygen requirement and is thermophilic, which reduces cooling cost.

C. acetobutylicum, also known as the 'Weizmann organism', was first used by Chaim Weizmann to produce acetone and biobutanol from starch in 1916 for the production of gunpowder and trinitrotoluene.

C. botulinum produces a potentially lethal neurotoxin used in a diluted form in the drug Botox, which is carefully injected to nerves in the face, which prevents the movement of the expressive muscles of the forehead, to delay the wrinkling effect of aging. It is also used to treat spasmodic torticollis and provides relief for around 12 to 16 weeks.

C. butyricum MIYAIRI 588 strain is marketed in Japan, Korea, and China for C. difficile prophylaxis due to its reported ability to interfere with the growth of the latter.

The anaerobic bacterium C. ljungdahlii, recently discovered in commercial chicken wastes, can produce ethanol from single-carbon sources including synthesis gas, a mixture of carbon monoxide and hydrogen, that can be generated from the partial combustion of either fossil fuels or biomass. Use of these bacteria to produce ethanol from synthesis gas has progressed to the pilot plant stage at the BRI Energy facility in Fayetteville, Arkansas.

Fatty acids are converted by yeasts to long-chain dicarboxylic acids and then to 1,3-propanediol using Clostridium diolis.

Genes from C. thermocellum have been inserted into transgenic mice to allow the production of endoglucanase. The experiment was intended to learn more about how the digestive capacity of monogastric animals could be improved.

Nonpathogenic strains of Clostridium may help in the treatment of diseases such as cancer. Research shows that Clostridium can selectively target cancer cells. Some strains can enter and replicate within solid tumors. Clostridium could, therefore, be used to deliver therapeutic proteins to tumours. This use of Clostridium has been demonstrated in a variety of preclinical models.

Mixtures of Clostridium species, such as C. beijerinckii, C. butyricum, and species from other genera have been shown to produce biohydrogen from yeast waste.

References

External links

• Clostridium genomes and related information at PATRIC, a Bioinformatics Resource Center funded by NIAID
• Todar's Online Textbook of Bacteriology
• UK Clostridium difficile Support Group
• Pathema-Clostridium Resource
• Water analysis: Clostridium video

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