Cell toxicity bacterial endotoxins

Endotoxins are bacterial cell envelope constituents that, when present in pharmaceutical products, cause pyrogenic reactions sometimes resulting in lethality. The toxicity of endotoxins is directly related to their chemical composition. However, the viability of the organism is irrelevant since endotoxin derived from dead or live microbes is equally active. The classical endotoxin is lipopolysaccharide (LPS). However, peptidoglycan (PG) also displays endotoxin-like activities. LPS is found only in gram-negative bacterial outer membranes, while PG is present in the cell... 

Lipopolysaccharides form a class of macromolecules unique to Gramnegative bacteria. They are of great compositional and structural diversity, and yet, they are built up according to a common architectural principle. With few exceptions, lipopolysaccharides are biologically highly active substances. Lipopolysaccharides have been called endotoxins because of their toxic properties. Due to the antigenic properties which they confer to the surface of the bacterial cell, they are also termed O antigens. 

A-B Toxins are bacterial toxins composed of two peptide chains one (B) that binds to the invaded cell surface, and the other (A) containing the toxin which is then taken-up into the cell. Some examples of exotoxins secreted by the bacteria into the surrounding medium and highly toxic to certain tissues are pathogens causing botuiism (Clostridium botulinum), tetanus (Clostridium tetani) and diptheria (Corynebacterium diphtheria. An example of an A-B endotoxin is Vibrio cholerae. Botulinum toxin and tetanus toxin have their main toxic actions on neuronal tissues, so are described at NEUROTOXINS. 

Endotoxins. Name for bacterial toxins which, in contrast to the exotoxins, are not secreted by living bacteria but are released from the cells by autolysis (e.g. in the intestines). In the case of classic E. they consist of the thermostable lipopolysaccharide (LPS-) fraction of the cell membrane anchored on the outer membranes of Gram-negative bacteria. The LPS consists of lipid A, the chain polysaccharide, and the O-specific chain lipid A is responsible for the toxic action of LPS. E. are found in all Enterobacteriaceae, e.g.. Salmonella (typhus), Shigella (dysentery), and many other Gramnegative pathogens. In the host organism E. stimulate mediators (cytokines) of the immune system. One of... 

A poison (toxin) that remains inside the microorganism which produced it. The toxicity is noted only when the bacterial cells are ruptured by mechanical or chemical means. Escherichia coll, Salmonella typhi and Shigella dysenteriae bacteria are known to form endotoxins. 

---