Lipopolysaccharides (LPS) are important outer membrane components of gram-negative bacteria. They are large amphipathic glycoconjugates that typically consist of a lipid domain (hydrophobic) attached to a core oligosaccharide and a distal polysaccharide. These molecules are also known as lipogylcans due to the presence of lipid and sugar molecules. The lipopolysaccharides are composed of:
Lipid A: the hydrophobic domain, which is an endotoxin and the main virulence factor
O-antigen, the repeating hydrophilic distal oligosaccharide
The hydrophilic core polysaccharide
The lipid A component varies from one organism to another and is essential in imparting specific pathogenic attributes to the bacteria. Inherent to gram-negative bacteria, LPS provides integrity to the bacterial cell and a mechanism of interaction of the bacteria to other surfaces. Most bacterial LPS molecules are thermostable and generate a robust pro-inflammatory stimulus for the immune system in mammals. Since different types of LPS are present in different genera of gram-negative bacteria, LPS is used for serotyping gram-negative bacteria. More specifically, the O-antigen imparts serological distinction to the bacterial species. Also, the size and composition of LPS are highly dynamic among bacterial species. Due to its unique properties, LPS has gained considerable research focus to understand its complex structure, biogenesis, transport, and assembly. Besides, LPS is also a recognized biomarker due to its central role in host-pathogen interaction that facilitates the infection process.
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