Clostridia
Encyclopedia
The Clostridia are a class of Firmicutes
, including Clostridium
and other similar genera. They are distinguished from the Bacilli
by lacking aerobic respiration. They are obligate anaerobe
s and oxygen is toxic to them. Species of the genus Clostridium are all Gram-positive and have the ability to form spores. Studies show they are not a monophyletic
group, and their relationships are not entirely certain. Currently most are placed in a single order called Clostridiales, but this is not a natural group and is likely to be redefined in the future.
Most species of the genus Clostridium are saprophytic organisms found in many places in the environment, most notably the soil. However, the genus does contain some human pathogens (outlined below).
The toxins produced by certain members of the Clostridium genus are among the most dangerous known to man. Examples are tetanus toxin (known as tetanospasmin
) produced by C. tetani and botulinum toxin produced by C. botulinum.
Notable species of this class include:
Heliobacteria
are also members of the class Clostridia.
Some of the enzymes produced by this group are used in bioremediation
.
Firmicutes
The Firmicutes are a phylum of bacteria, most of which have Gram-positive cell wall structure. A few, however, such as Megasphaera, Pectinatus, Selenomonas and Zymophilus, have a porous pseudo-outer-membrane that causes them to stain Gram-negative...
, including Clostridium
Clostridium
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 or spindle...
and other similar genera. They are distinguished from the Bacilli
Bacilli
Bacilli refers to a taxonomic class of bacteria. It includes two orders, Bacillales and Lactobacillales, which contain several well-known pathogens like Bacillus anthracis .-Ambiguity:...
by lacking aerobic respiration. They are obligate anaerobe
Obligate anaerobe
Obligate anaerobes are microorganisms that live and grow in the absence of molecular oxygen; some of these are killed by oxygen. -Metabolism:...
s and oxygen is toxic to them. Species of the genus Clostridium are all Gram-positive and have the ability to form spores. Studies show they are not a monophyletic
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
group, and their relationships are not entirely certain. Currently most are placed in a single order called Clostridiales, but this is not a natural group and is likely to be redefined in the future.
Most species of the genus Clostridium are saprophytic organisms found in many places in the environment, most notably the soil. However, the genus does contain some human pathogens (outlined below).
The toxins produced by certain members of the Clostridium genus are among the most dangerous known to man. Examples are tetanus toxin (known as tetanospasmin
Tetanospasmin
Tetanus toxin is an extremely potent neurotoxin produced by the vegetative cell of Clostridium tetani in anaerobic conditions, causing tetanus. It has no known function for clostridia in the soil environment where they are normally encountered. It is also called spasmogenic toxin, tetanospasmin or...
) produced by C. tetani and botulinum toxin produced by C. botulinum.
Notable species of this class include:
- Clostridium perfringensClostridium perfringensClostridium perfringens is a Gram-positive, rod-shaped, anaerobic, spore-forming bacterium of the genus Clostridium. C. perfringens is ever present in nature and can be found as a normal component of decaying vegetation, marine sediment, the intestinal tract of humans and other vertebrates,...
(GangreneGangreneGangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...
, Food poisoning) - Clostridium difficileClostridium difficileClostridium difficile , also known as "CDF/cdf", or "C...
(Pseudomembranous colitisPseudomembranous colitisPseudomembranous colitis, a cause of antibiotic-associated diarrhea , is an infection of the colon. It is often, but not always, caused by the bacterium Clostridium difficile. Because of this, the informal name C. difficile colitis is also commonly used. The illness is characterized by...
) - Clostridium tetaniClostridium tetaniClostridium tetani is a rod-shaped, anaerobic bacterium of the genus Clostridium. Like other Clostridium species, it is Gram-positive, and its appearance on a gram stain resembles tennis rackets or drumsticks. C. tetani is found as spores in soil or in the gastrointestinal tract of animals. C...
(TetanusTetanusTetanus is a medical condition characterized by a prolonged contraction of skeletal muscle fibers. The primary symptoms are caused by tetanospasmin, a neurotoxin produced by the Gram-positive, rod-shaped, obligate anaerobic bacterium Clostridium tetani...
) - Clostridium botulinumClostridium botulinumClostridium botulinum is a Gram-positive, rod-shaped bacterium that produces several toxins. The best known are its neurotoxins, subdivided in types A-G, that cause the flaccid muscular paralysis seen in botulism. It is also the main paralytic agent in botox. C. botulinum is an anaerobic...
(BotulismBotulismBotulism also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin which is metabolic waste produced under anaerobic conditions by the bacterium Clostridium botulinum, and affecting a wide range of mammals, birds and fish...
) - Clostridium acetobutylicumClostridium acetobutylicumClostridium acetobutylicum, ATCC 824, is included in the genus Clostridium, is a commercially valuable bacterium sometimes called the "Weizmann Organism", after Jewish-Russian born Chaim Weizmann, then senior lecturer at the University of Manchester, England, used them in 1916 as a bio-chemical...
- Clostridium haemolyticum
- Clostridium novyiClostridium novyiClostridium novyi a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals. It comes in three types, labelled A, B, and a non-pathogenic...
- Clostridium oedematiensClostridium novyiClostridium novyi a Gram-positive, endospore- forming, obligate anaerobic bacteria of the class clostridia. It is ubiquitous, being found in the soil and faeces. It is pathogenic, causing a wide variety of diseases in man and animals. It comes in three types, labelled A, B, and a non-pathogenic...
Heliobacteria
Heliobacteria
The heliobacteria are phototrophic, that is to say, they convert light energy into chemical energy by photosynthesis; they use a PSI type reaction center. The primary pigment involved is bacteriochlorophyll g, which is unique to the group and has a unique absorption spectrum; this gives the...
are also members of the class Clostridia.
Some of the enzymes produced by this group are used in bioremediation
Bioremediation
Bioremediation is the use of microorganism metabolism to remove pollutants. Technologies can be generally classified as in situ or ex situ. In situ bioremediation involves treating the contaminated material at the site, while ex situ involves the removal of the contaminated material to be treated...
.