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 Greekkloster (κλωστήρ) or spindle. These characteristics traditionally defined the genus; however many species originally classified as Clostridium have been reclassified in other genera.
Clostridium consists of around 100 species that include common free-living bacteria as well as important pathogens. There are five main species responsible for disease in humans.
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. tetani, the causative organism of tetanus. The name is derived from Ancient Greek: τέτανοςtetanos “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. Less than one case per year has been reported since 2000.
Clostridium 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.
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.
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 that highly pathogenic organism.
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.
Mixtures of Clostridium species, such as a mixtures of C. beijerinckii, C. butyricum, and species from other genera have been shown to produce biohydrogen from yeast waste.
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:
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.
^Ryan KJ, Ray CG (editors) (2004). Sherris Medical Microbiology (4th ed.). McGraw Hill. ISBN0-8385-8529-9.
^Bruggemann H, Gottschalk G (editors). (2009). Clostridia: Molecular Biology in the Post-genomic Era. Caister Academic Press. ISBN978-1-904455-38-7.