Lipopolysaccharides: Bacterial Toxins and Health Impact

• Lipopolysaccharides are large molecules consisting of a lipid and a polysaccharide that are bacterial toxins.
• The term endotoxin is often used synonymously with LPS, although there are a few endotoxins (in the original sense of toxins that are inside the bacterial cell that are released when the cell disintegrates) that are not related to LPS, such as the so-called delta endotoxin proteins produced by Bacillus thuringiensis.
• LPS can have substantial impacts on human health, primarily through interactions with the immune system.
• LPS is a potent activator of the immune system and pyrogen (agent that causes fever).
• In severe cases, LPS can play a role in causing septic shock.
• In lower levels and over a longer time period, there is evidence LPS may play an important and harmful role in autoimmunity, obesity, depression, and cellular senescence.
• Discovery[edit]
• The toxic activity of LPS was first discovered and termed endotoxin by Richard Friedrich Johannes Pfeiffer.
• He distinguished between exotoxins, toxins that are released by bacteria into the surrounding environment, and endotoxins, which are toxins "within" the bacterial cell and released only after destruction of the bacterial outer membrane.
• Subsequent work showed that release of LPS from gram negative microbes does not necessarily require the destruction of the bacterial cell wall, but rather, LPS is secreted as part of the normal physiological activity of membrane vesicle trafficking in the form of bacterial outer membrane vesicles (OMVs), which may also contain other virulence factors and proteins.
• LPS is a major component of the outer membrane of Gram-negative bacteria, contributing greatly to the structural integrity of the bacteria and protecting the membrane from certain kinds of chemical attack.
• LPS is the most abundant antigen on the cell surface of most Gram-negative bacteria, contributing up to 80% of the outer membrane of E. coli and Salmonella.
• LPS increases the negative charge of the cell membrane and helps stabilize the overall membrane structure.
• It is of crucial importance to many Gram-negative bacteria, which die if the genes coding for it are mutated or removed.
• However, it appears that LPS is nonessential in at least some Gram-negative bacteria, such as Neisseria meningitidis, Moraxella catarrhalis, and Acinetobacter baumannii.
• LPS is also required for the functioning of omptins, a class of bacterial protease.
• Composition[edit]
• Lipopolysaccharides are composed of three parts: The O antigen (or O polysaccharide), the Core oligosaccharide, and Lipid A.
• Kdo2-Lipid A is the most abundant

Test your knowledge on lipopolysaccharides (LPS) - large bacterial toxins with substantial impacts on human health, primarily through interactions with the immune system. Learn about their discovery, composition, and the role they play in autoimmune diseases, obesity, depression, and cellular senescence.