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Genus of Gram-positive bacteria, which includes several significant human pathogens
This article may require cleanup to meet Wikipedia's quality standards. The specific problem is: need to move many subdivisions away (Hathewaya/Cluster II [Lawson and Rainey 2016], Sedimentibacter, Enterocloster, Lacrimispora, many other reclassifications) and move content into Firmicutes, Clostridia, or Clostridiaceae as appropriate; 250 species count is fishy, and so is grouping C. with Bacillus. Please help improve this article if you can.(December 2020) (Learn how and when to remove this template message)
Clostridium is a genus of Gram-positive bacteria. This genus includes several significant human pathogens, including the causative agents of botulism and tetanus. The genus formerly included an important cause of diarrhea, Clostridioides difficile, which was reclassified into the Clostridiodies genus in 2016. They are obligate anaerobes capable of producing endospores. The normal, reproducing cells of Clostridium, called the vegetative form, are rod-shaped, which gives them their name, from the Greek ? or spindle. Clostridium endospores have a distinct bowling pin or bottle shape, distinguishing them from other bacterial endospores, which are usually ovoid in shape. Clostridium species inhabit soils and the intestinal tract of animals, including humans.Clostridium is a normal inhabitant of the healthy lower reproductive tract of females.
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 and its close relatives. Over the years, this has resulted in many new genera being split out, with the ultimate goal of constraining Clostridium to cluster I.
"Clostridium" cluster XIVa and "Clostridium" cluster IV efficiently ferment plant polysaccharide composing dietary fiber, making them important and abundant taxa in the rumen and the human large intestine. As mentioned before, these clusters are not part of current Clostridium, and use of these terms should be avoided due to ambiguous or inconsistent usage.
Pathogenesis and classification
Clostridium contains around 250 species that include common free-living bacteria, as well as important pathogens. The main species responsible for disease in humans are:
Clostridium sordellii (now Paeniclostridium) can cause a fatal infection in exceptionally rare cases after medical abortions.
Bacillus and Clostridium are often described as Gram-variable, because they show an increasing number of gram-negative cells as the culture ages.
Clostridium and Bacillus are both in the phylumFirmicutes, but they are in different classes, orders, and families. Microbiologists distinguish Clostridium from Bacillus by the following features:
Clostridium grows in anaerobic conditions; Bacillus grows in aerobic conditions.
Clostridium forms bottle-shaped endospores; Bacillus forms oblong endospores.
Clostridium does not form the enzyme catalase; Bacillus secretes catalase to destroy toxic byproducts of oxygen metabolism.
Clostridium and Desulfotomaculum are both in the class Clostridia and order Clostridiales, and they both produce bottle-shaped endospores, but they are in different families. Clostridium can be distinguished from Desulfotomaculum on the basis of the nutrients each genus uses (the latter requires sulfur).
The vegetative cells of clostridia are heat-labile and are killed by short heating at temperatures above 72-75 °C. The thermal destruction of Clostridium spores requires higher temperatures (above 121.1 °C, for example in an autoclave) and longer cooking times (20 min, with a few exceptional cases of > 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 irradiated foods for general use in the retail market. The addition of lysozyme, nitrate, nitrite and propionic acid salts inhibits clostridia in various foods.
In the late 1700s, Germany experienced a number of outbreaks of an illness that seemed connected to eating certain 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. The mechanisms of anaerobic respiration were still not yet well elucidated at that time, so taxonomy of anaerobes was still nascent.
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.
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.
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.
^Meites E, Zane S, Gould C (September 2010). "Fatal Clostridium sordellii infections after medical abortions". The New England Journal of Medicine. 363 (14): 1382-3. doi:10.1056/NEJMc1001014. PMID20879895.
^ abcTortora GJ, Funke BR, Case CL (2010), Microbiology: An Introduction (10th ed.), Benjamin Cummings, pp. 87, 134, 433, ISBN978-0-321-55007-1