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This chapter presents a brief outline of our current knowledge of the structures of the bounding ... more This chapter presents a brief outline of our current knowledge of the structures of the bounding membranes (the inner and the outer membranes and the intermediate periplasmic layer) of a Gram-negative bacterial cell. Also the structure and chemical composition of the outer membrane vesicles (OMVs) originating from the surface of these bacteria including their proteomic profile, as obtained mainly by mass spectroscopic and related studies, have been presented in brief. The Gram-negative bacteria are usually bounded by two membranous structures (Fig. 2.1). The inner one (IM), called the plasma membrane, is a trilamellar structure that bounds the bacterial protoplasm and is composed of a phospholipids bilayer. The outer membrane (OM) also presents a trilamellar structure (with two electron dense leaflets, outer and inner) in the electron micrograph and consists of proteins, including porins, receptors, and an asymmetric distribution of lipids. The outer leaflet is composed primarily of lipopolysaccharide (LPS) projecting outside and the inner leaflet containing phospholipids and lipoproteins. The LPS of a Gram-negative bacterium consists of three different sectors: (i) lipid-A, (ii) the core polysaccharide comprising the inner and the outer cores, and (iii) the O-specific polysaccharide chains (Fig. 2.1) projecting outward. The lipid portion of LPS serves as the lipid anchor and is commonly composed of fatty acids, sugars, and phosphate groups. The chemical structures of lipid-A, core polysaccharide, and O-specific polysaccharide chains of Vibrio cholerae are shown in Fig. 2.2 a, b,
This chapter presents a brief outline of our current knowledge of the structures of the bounding ... more This chapter presents a brief outline of our current knowledge of the structures of the bounding membranes (the inner and the outer membranes and the intermediate periplasmic layer) of a Gram-negative bacterial cell. Also the structure and chemical composition of the outer membrane vesicles (OMVs) originating from the surface of these bacteria including their proteomic profile, as obtained mainly by mass spectroscopic and related studies, have been presented in brief. The Gram-negative bacteria are usually bounded by two membranous structures (Fig. 2.1). The inner one (IM), called the plasma membrane, is a trilamellar structure that bounds the bacterial protoplasm and is composed of a phospholipids bilayer. The outer membrane (OM) also presents a trilamellar structure (with two electron dense leaflets, outer and inner) in the electron micrograph and consists of proteins, including porins, receptors, and an asymmetric distribution of lipids. The outer leaflet is composed primarily of lipopolysaccharide (LPS) projecting outside and the inner leaflet containing phospholipids and lipoproteins. The LPS of a Gram-negative bacterium consists of three different sectors: (i) lipid-A, (ii) the core polysaccharide comprising the inner and the outer cores, and (iii) the O-specific polysaccharide chains (Fig. 2.1) projecting outward. The lipid portion of LPS serves as the lipid anchor and is commonly composed of fatty acids, sugars, and phosphate groups. The chemical structures of lipid-A, core polysaccharide, and O-specific polysaccharide chains of Vibrio cholerae are shown in Fig. 2.2 a, b,