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; however many species originally classified as Clostridium have been reclassified in other genera.
- C. botulinum, an organism that produces botulinum toxin in food/wound and can cause botulism. Honey sometimes contains spores of Clostridium 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 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, which 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. Also responsible for 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, the causative organism of tetanus. The name derives from the Greek word τέτανος (tetanos) "muscular spasm", due to the violent spasms caused by C. tetani infection.
- C. sordellii can cause a fatal infection in exceptionally rare cases after medical abortions. Less than one case per year has been reported since 2000.
Neurotoxin production is the unifying feature of the species C. botulinum. Seven types of toxins have been identified and allocated a letter (A-G). 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.
C. thermocellum can utilize 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. botulinum produces a potentially lethal neurotoxin that is 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 ageing. It is also used to treat spasmodic torticollis and provides relief for approximately 12 to 16 weeks.
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.
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. Hall et al. published their findings in 1993.
Non-pathogenic 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 tumours. Clostridium could, therefore, be used to deliver therapeutic proteins to tumours. This use of Clostridium has been demonstrated in a variety of preclinical models.
This genus like several others has undergone a number of revisions with the increasing availability of genomic data. An analysis of a number of proteins from a number of members of this genus has suggested another revision. The main findings of this study were:
- Clostridium difficile and its close relatives are members of the family Peptostreptococcaceae
- Members of the family Ruminococcaceae belong to the genus Clostridium
It has been proposed to create six new genera accommodate the 78 validly described species that do not appear to be Clostridia. These genera are: Erysipelatoclostridium, Gottschalkia, Lachnoclostridium, Peptoclostridium, Ruminiclostridium and Tyzzerella.
Under this proposal the species Clostridium difficile would become Peptoclostridium difficle.
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