Clostridium is a genus of anaerobic, Gram-positive bacteria. Species of Clostridium inhabit soils and the intestinal tracts of animals, including humans.
History
In the late 1700s, Germany experienced several outbreaks of an illness connected to eating specific sausages. In 1817, the German neurologist
Justinus Kerner detected rod-shaped cells in his investigations into this so-called sausage poisoning. In 1897, the Belgian biology professor Emile van Ermengem published his finding of an endospore-forming organism he isolated from spoiled ham. Biologists classified van Ermengem's discovery along with other known gram-positive spore formers in the genus
Bacillus. This classification presented problems, however, because the isolate grew only in anaerobic conditions, but
Bacillus grew well in oxygen.
Circa 1880, in the course of studying fermentation and butyric acid synthesis, a scientist surnamed Prazmowski first assigned a binomial name to Clostridium butyricum.
In 1924, Ida A. Bengtson separated van Ermengem's microorganisms from the Bacillus group and assigned them to the genus Clostridium. By Bengtson's classification scheme, Clostridium contained all of the anaerobic endospore-forming rod-shaped bacteria, except the genus Desulfotomaculum.
Taxonomy
As of October 2022, there are 164 validly published species in
Clostridium.
[Page Genus: Clostridium on ]
The genus, as traditionally defined, contains many organisms not closely related to its type species. The issue was originally illustrated in full detail by a rRNA phylogeny from Collins 1994, which split the traditional genus (now corresponding to a large slice of Clostridia) into twenty clusters, with cluster I containing the type species Clostridium butyricum and its close relatives.
"Clostridium" cluster XIVa (now Lachnospiraceae)
Biochemistry
Species of
Clostridium are obligate anaerobe and capable of producing
. They generally stain gram-positive, but as well as
Bacillus, are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages.
The normal, reproducing cells of
Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek κλωστήρ or spindle.
Clostridium endospores have a distinct bowling pin or bottle shape, distinguishing them from other bacterial endospores, which are usually ovoid in shape. The Schaeffer–Fulton stain (0.5%
malachite green in water) can be used to distinguish endospores of
Bacillus and
Clostridium from other microorganisms.
Clostridium can be differentiated from the also endospore forming genus Bacillus by its obligate anaerobic growth, the shape of endospores and the lack of catalase. Species of Desulfotomaculum form similar endospores and can be distinguished by their requirement for sulfur.
There is a commercially available polymerase chain reaction (PCR) test kit (Bactotype) for the detection of C. perfringens and other pathogenic bacteria.
Biology and pathogenesis
Clostridium species are readily found inhabiting soils and intestinal tracts.
Clostridium species are also a normal inhabitant of the healthy lower reproductive tract of females.
The main species responsible for disease in humans are:
Several more pathogenic species, that were previously described in Clostridium, have been found to belong to other genera.[
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Clostridium difficile, now placed in Clostridioides.
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Clostridium histolyticum, now placed in Hathewaya.
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Clostridium sordellii, now placed in Paraclostridium, can cause a fatal infection in exceptionally rare cases after medical abortions.
Treatment
In general, the treatment of clostridial infection is high-dose penicillin G, to which the organism has remained susceptible.
The vegetative cells of clostridia are heat-labile and are killed by short heating at temperatures above . The thermal destruction of Clostridium spores requires higher temperatures (above , for example in an autoclave) and longer cooking times (20 min, with a few exceptional cases of more than 50 min recorded in the literature). Clostridia and Bacilli are quite radiation-resistant, requiring doses of about 30 kGy, which is a serious obstacle to the development of shelf-stable for general use in the retail market.
Fructooligosaccharides () such as inulin, occurring in relatively large amounts in a number of foods such as chicory, garlic, onion, leek, artichoke, and asparagus, have a prebiotic or Bifidus factor effect, selectively promoting the growth and metabolism of beneficial bacteria in the Large intestine, such as Bifidobacteria and Lactobacilli, while inhibiting harmful ones, such as clostridia, fusobacteria, and Bacteroides.
Use
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Clostridium 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 Thermophile, which reduces cooling cost.
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Clostridium acetobutylicum was first used by Chaim Weizmann to produce acetone and biobutanol from starch in 1916 for the production of cordite (smokeless gunpowder) in the Weizmann process.
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Clostridium 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.
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Clostridium butyricum strain MIYAIRI 588 is marketed in Japan, Korea, and China for Clostridium difficile prophylaxis due to its reported ability to interfere with the growth of the latter.
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Clostridium histolyticum has been used as a source of the enzyme collagenase, which degrades animal tissue. Clostridium species excrete collagenase to eat through tissue and, thus, help the pathogen spread throughout the body. The medical profession uses collagenase for the same reason in the débridement of infected wounds.
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Clostridium 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 or biomass.
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Clostridium butyricum converts glycerol to 1,3-propanediol.
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Genes from Clostridium 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.
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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 . Clostridium could, therefore, be used to deliver therapeutic proteins to tumours. This use of Clostridium has been demonstrated in a variety of preclinical models.
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Mixtures of Clostridium species, such as Clostridium beijerinckii, Clostridium butyricum, and species from other genera have been shown to produce biohydrogen from yeast waste.
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