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Encyclopedia > Endotoxins

Endotoxin is part of the outer membrane of the cell wall of Gram-negative bacteria. It refers to the lipopolysaccharide (LPS) complex associated with the outer membrane of Gram-negative bacteria. LPS is also called endotoxin, owing to its historical discovery. In the 1800s it became understood that bacteria could secrete toxins into their environment, which became broadly known as "exotoxin". The term endotoxin comes from the discovery that portions of Gram-negative bacteria itself can cause toxicity, hence the name endotoxin. Studies of endotoxin over the next 50 years revealed that the actual molecule responsible for the effects of "endotoxin" was in fact lipopolysaccharide. A cell wall is a more or less solid layer surrounding a cell. ... Bacteria that are Gram-negative are not stained dark blue or violet by Gram staining, in contrast to Gram-positive bacteria. ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria(singular, bacterium) are a major group of living organisms. ... A lipopolysaccharide (LPS) is a large molecule that contains both lipid and a carbohydrate. ... An exotoxin is a soluble chemical excreted by a microorganism, including bacteria, fungi, algae, and protozoa. ... Toxicity (from Greek τοξικότητα - poisonousness) is a measure to the degree to which something is toxic or poisonous. ...


Endotoxins consist of a polysaccharide ("sugar") chain and a lipid moiety, known as lipid A, which is reponsible for the toxic effects. The polysaccharide chain is highly variable amongst different bacteria. Humans are able to produce antibodies to endotoxins after exposure, but these are generally directed at the polysaccharide chain, and do not protect against a wide variety of endotoxins. Injection of a small amount of endotoxin in human volunteers produced fever, a lowering of the blood pressure, and activation of inflammation and coagulation. Endotoxins are in large part responsible for the dramatic clinical manifestations of infections with pathogenic Gram-negative bacteria, such as Neisseria meningitides (that causes fulminant meningitis). Polysaccharides (sometimes called glycans) are relatively complex carbohydrates. ... Meningitis is inflammation of the membranes (meninges) covering the brain and the spinal cord. ...


LPS has been demonstrated to bind to Toll-like receptor-4 of several immune system cells (including macrophages and dendritic cells), triggering the signalling cascade for macrophage/endothelial cells to secrete pro-inflammatory cytokines. The binding to TLR-4 requires the presence of the serum factor Lipopolysaccharide Binding Protein (LBP). Toll-like receptors (TLRs) are type I transmembrane proteins that serve as a key part of the innate immune system. ... The immune system is the system of specialised cells and organs that protect an organism from outside biological influences. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... Dendritic cells (DC) are immune cells and form part of the mammal immune system. ... Macrophages (Greek: big eaters) are cells found in tissues that are responsible for phagocytosis of pathogens, dead cells and cellular debris. ... The endothelium is the layer of thin, flat cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. ... Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ... Cytokines are small protein molecules that are the core of communication between immune system cells, and even between these cells and cells belonging to other tissue types. ...


Endotoxins are frequent contaminants in plasmid DNA prepared from bacteria, and must be removed from the DNA to avoid unwanted inflammatory responses prior to in vivo applications such as gene therapy. Figure 1 : Schematic drawing of a bacterium with plasmids enclosed. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and most viruses). ... Phyla/Divisions Actinobacteria Aquificae Bacteroidetes/Chlorobi Chlamydiae/Verrucomicrobia Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Nitrospirae Omnibacteria Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Bacteria (singular, bacterium) are a major group of living organisms. ... Gene therapy using an Adenovirus vector. ...


In pharmaceutical production, it is necessary to remove all traces of endotoxin from drug product containers, as even small amounts of endotoxin will cause illness in humans (but not disease). A depyrogenation oven is used for this purpose. Temperatures of approximately 400 degrees celsius are required to break down this substance.


External links

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  Results from FactBites:
 
Endotoxin (2220 words)
Endotoxins are part of the outer membrane of the cell wall of Gram-negative bacteria.
Endotoxins are invariably associated with Gram-negative bacteria whether the organisms are pathogens or not.
Endotoxins are toxic to most mammals, and regardless of the bacterial source, all endotoxins produce the same range of biological effects in the animal host.
Endotoxin Activity Assay for the diagnosis of Sepsis (272 words)
Endotoxin Activity Assay for the diagnosis of Sepsis
The EAA™ Endotoxin Activity Assay is the only FDA approved rapid whole blood assay for detection of human endotoxemia.
Endotoxin is the most important microbial trigger for sepsis.
  More results at FactBites »

 
 

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