Endotoxin

Endotoxins ( ancient Greek endo ἐndo: "inside", "inside", τοξίνη, toxins, " toxic substance" ) are a class of naturally occurring chemical compounds. They are decay products of bacteria that can trigger numerous physiological reactions in humans.

Definition

Endotoxins are a component of the outer membrane (OM = outer membrane ) of Gram-negative bacteria or cyanobacteria. Chemically it lipopolysaccharides (LPS), which are composed of a hydrophilic polysaccharide, and a lipophilic lipid content. In contrast to the bacteria from which they originate, endotoxins are very heat stable and even survive the sterilization.

Word origin

The term endotoxin (as opposed to ectotoxin or exotoxin ) is derived from the Greek endo = inside and toxin = poison because their discoverer Richard Pfeiffer mistakenly assumed they would be released from inside the bacteria.

Effects

Endotoxins are among the pyrogens, which means they can produce fever in contact with mucous membranes, and in crossing the blood in humans and some animal species. They also activate a number of signaling pathways of immunocompetent cells, which can lead these cells to either an inflammation or to a programmed cell death ( apoptosis). You are already at very low concentrations (low pg / ml range ) biologically active. The LD50 value is endotoxins at 200-400 micrograms per mouse (compared to exotoxins: LD50 value of 25 pg ). Endotoxins are not continuously released primarily in the free cell lysis, but unlike enterotoxins or exotoxins of live bacteria into the surrounding medium.

Detection and determination

The most sensitive method of measuring endotoxin works on the activation of the coagulation cascade in the amebocyte lysate of the horseshoe crabs from (Limulus polyphemus ) were isolated (known LAL assay ). More modern methods now renounce the use of animal components and use them for the endotoxin recombinant proteins that are able to bind to endotoxins and at the same time are capable of conversion of a substrate to generate a fluorescent signal.

Destruction of endotoxins

Heat-resistant devices can be freed with 5 hours at 200 ° C of the endotoxins, and non-heat -resistant equipment with 1 molar sodium hydroxide solution, which is to stand for 15 hours.