![]() ![]() Virulence depends on the core and O-antigen domains, which, consequently, are present in most clinical isolates.Ī representative structure of lipid A from Escherichia coli. These complex glycoforms are dispensable for growth but are required for the integrity of bacteria and to protect them from complement-mediated lysis and antibiotics. With a few exceptions, the lipid A and Kdo domains are important for the proper growth of bacteria. It is a glucosamine-based saccharolipid that constitutes the outer leaflet of the external membranes of most Gram-negative bacteria. Lipid A (also known as endotoxin) is a unique and distinctive hydrophobic segment that anchors the LPS to the membrane ( Figure 2). The O-antigen is appended to the core oligosaccharide (core-OS), which shows less variation and possesses particular saccharide units however, some other groups in core-OS have also been reported in this region. ![]() The O-antigens are anionic, which facilitates the survival of these bacteria in oceanic environments. In general, LPS is a conserved molecule with minor modifications for instance, bacteria can be classified into different serotypes and serovars according to the degree of polymerization of S-type LPS. Gal, galactose GalNac, N-acetyl-galactosamine Glc, glucose GlcN, glucosamine Hep, l-glycero- d-mannoheptose Kdo, 3-deoxy- d-manno-2-octulonic acid Man, mannose NAG, N-acetyl-glucosamine. On the basis of the presence of the oligosaccharide, LPS can be classified into smooth, rough, and semi-rough types that pose different levels of threat during infection. ![]() LPS can be divided into three regions: O-antigen, core region, and lipid A. ![]() Īn overview of the complete LPS structure. The polar residues in LPS, e.g., the polar head groups of phospholipids, are vital for the structural morphology and physiology of the outer membrane of bacteria. Anionic groups such as Kdo, phosphates, and other acidic residues are commonly present on the inner core region and lipid A. Classically, lipid A is a dimer of d-glucosamine ( d-GlcN) monomers linked in a β-1,6 fashion, to which fatty acid chains, typically 3-hydroxyalkanoic acids, are linked by amide or ester bonds. The core consists of 3-deoxy- d-manno-2-octulosonic acid (Kdo) and l-glycero- d-manno-heptose ( l, d-Hep). S-type LPS has additional components and is regarded as the most complete form that can be further subdivided into three parts in which (1) the O-antigenic outer region (generally a polymer of oligosaccharide units) is attached to (2) the hydrophobic membrane anchor, lipid A, by (3) a linker oligosaccharide known as the core. Currently, there is considerable research interest in determining the chemical features of LPS from Gram-negative bacteria thriving in marine environments.īased on its appearance and composition, LPS can be divided into two types: smooth (S-type) and rough (R-type) ( Figure 1). LPS from non-pathogenic bacteria has been studied in detail to discover new therapeutics to combat lethal bacterial infections. Gram-negative bacteria are characterized by the presence of a unique cell wall component termed lipopolysaccharide (LPS), which is associated with substantial diseases in humans and marine organisms. In recent years, much research attention has been devoted to isolating different metabolic intermediates and pathways as possible targets to treat diseases. The marine environment is enriched with bacteria that provide a fruitful source of natural substances, including antibiotics, antitumor agents, antitoxins, and enzymes, which have a broad range of applications. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |