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Clostridium, genus of gram-positive bacteria (see Gram's stain), several species of which cause significant, potentially deadly diseases in humans as a result of the toxins that each produces. Clostridium bacteria are rod-shaped and anaerobic, that is, they live in the absence of oxygen; they are common in the soil. C. botulinum, which grows in improperly canned food, produces neurotoxins that when ingested cause the form of food poisoning known as botulism. C. difficile, commonly known as C. diff, is usually transmitted in hospitals and nursing homes as a result of poor personal hygiene and insufficient disinfection; a person taking antibiotics, which kills normal intestinal bacteria, is more susceptible to the bacterium. Infection may cause fever, nausea and abdominal pain, diarrhea, and, in more severe cases, colitis. Infection is most deadly in those over 65 years of age. Since 2001 a more virulent and drug-resistant strain has of C. difficile has developed, making infection increasingly difficult to treat. Treatment typically involves stopping the antibiotic that promoted the infection and taking the antibiotics metronidazole (Flagyl; in milder cases) or vancomycin (in more severe cases); in the most extreme cases, the colon may be surgically removed. C. perfringens infection causes gas gangrene; it generally occurs in the body where trauma, surgery, or another cause has resulted in diminished blood supply. Within a week, fever and pain at the infection site results as the toxins released by the bacteria kill muscle cells; if untreated, muscle necrosis rapidly develops and spreads, leading to death. Tetanus results when C. tetani infects body tissues through a puncture wound or trauma. C. tetani is common in the digestive tract, but its toxins are destroyed digestive enzymes.
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A genus of bacteria comprising large anaerobic spore-forming rods that usually stain gram-positive. Most species are anaerobes, but a few will grow minimally in air at atmospheric pressure.

The clostridia are widely distributed in nature, and are present in the soil and in the intestinal tracts of humans and animals. They usually live a saprophytic existence, and play a major role in the degradation of organic material in the soil and other nature environments. A number of clostridia release potent exotoxins and are pathogenic for humans and animals. Among the human pathogens are the causative agents of botulism (Clostridium botulinum), tetanus (C. tetani), gas gangrene (C. perfringens), and an antibiotic-associated enterocolitis (C. difficile). See Anaerobic infection, Botulism, Toxin

Clostridial cells are straight or slightly curved rods, 0.3–1.6 micrometers wide and 1–14 μm long. They may occur singly, in pairs, in short or long chains, or in helical coils. The length of the cells of the individual species varies according to the stage of growth and growth conditions. Most clostridia are motile with a uniform arrangement of flagella. See Cilia and flagella

The endospores produced by clostridia are dormant structures capable of surviving for prolonged periods of time, and have the ability to reestablish vegetative growth when appropriate environmental conditions are provided. The spores of clostridia are oval or spherical and are wider than the vegetative bacterial cell. Among the distinctive forms are spindle-shaped organisms, club-shaped forms, and tennis racket-shaped structures:

Clostridia are obligate anaerobes: they are unable to use molecular oxygen as a final electron acceptor and generate their energy solely by fermentation. Clostridia exhibit varying degrees of intolerance of oxygen. Some species are sensitive to oxygen concentrations as low as 0.5%, but most species can tolerate concentrations of 3–5%. The sensitivity of clostridia to oxygen restricts their habitat to anaerobic environments; habitats that contain large amounts of organic matter provide optimal conditions for their growth and survival.

A primary property of all species of Clostridium is their inability to carry out a dissimilatory reduction of sulfate. Most species are chemoorganotrophic. The substrate spectrum for the genus as a whole is very broad and includes a wide range of naturally occurring compounds. Extracellular enzymes are secreted by many species, enabling the organism to utilize a wide variety of complex natural substrates in the environment.

McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a genus of spore-bearing bacteria, first described in 1880 by the Polish microbiologist A. Prazmowski. The genus Clostridium includes all bacteria whose cells swell at the center during the process of sporulation and take on a spindle shape. Most of the bacteria in the group are anaerobes and are capable of fermenting various hydrocarbons. Included in the genus are the causative agents of acetobutylic fermentation, retting, tetanus, botulism, and gas gangrene.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


A genus of bacteria in the family Bacillaceae; usually motile rods which form large spores that distend the cell; anaerobic and do not reduce sulfate.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
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