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#lipopolysaccharide

3 public questions tagged with this topic.

Microbial Physiology

Which component of the Gram-negative bacterial cell wall is responsible for its endotoxin activity?

Lipopolysaccharide defines outer leaflet of Gram-negative outer membrane and accounts for barrier properties and immune activation. Its lipid anchor, lipid A, determines endotoxin activity, while core polysaccharide and distal O-antigen provide antigenic variation. Lipid A consists of diglucosamine bisphosphate hexa-acylated with hydroxy fatty acids, a unique pathogen-associated molecular pattern detected by host innate receptor TLR4/MD-2 complex. Upon release during cell division, death, or antibiotic-induced lysis, lipid A stimulates macrophages to secrete potent mediators like tumor necrosi

Ref: Raetz & Whitfield, Ann Rev Biochem 2002, LPS Endotoxins; Erridge et al., Microbes Infect 2002, Endotoxin Structure.

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Microbial Physiology

Which component gives Gram-negative bacteria endotoxic properties?

The outer leaflet of Gram-negative outer membrane is dominated by lipopolysaccharide, a high-molecular-weight amphipathic complex consisting of variable O-antigen polysaccharide, conserved core oligosaccharide containing 3-deoxy-D-manno-octulosonate (Kdo), and hydrophobic lipid A anchor. Lipid A is the endotoxic principle. Chemically it is a beta-1,6-linked D-glucosamine disaccharide phosphorylated at positions 1 and 4 prime and hexa-acylated with 3-hydroxy fatty acids in Escherichia coli, a structure absent from mammalian membranes. This moiety serves as a classic pathogen-associated molecula

Ref: Raetz & Whitfield, Ann Rev Biochem 2002, LPS Endotoxins; Janeway's Immunobiology, 9th ed., Recognition of LPS.

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Immunology

Which TLR recognizes bacterial lipopolysaccharide (LPS)?

Toll-like receptor 4, in complex with MD-2, is the primary sensor for bacterial lipopolysaccharide. Ligand binding triggers both MyD88-dependent and TRIF-dependent signaling pathways that culminate in NF-κB activation and type-I interferon production. The resulting inflammatory response is essential for host defense yet can also drive septic shock when excessive. Careful

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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