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In other Archaea, such as Methanomicrobium and Desulfurococcus, the wall may be composed only of surface-layer proteins, [12] known as an S-layer. S-layers are common in bacteria, where they serve as either the sole cell-wall component or an outer layer in conjunction with polysaccharides. Most Archaea are Gram-negative, though at least one ...
The glycocalyx (pl.: glycocalyces or glycocalyxes), also known as the pericellular matrix and cell coat, is a layer of glycoproteins and glycolipids which surround the cell membranes of bacteria, epithelial cells, and other cells. [1] Animal epithelial cells have a fuzz-like coating on the external surface of their plasma membranes.
An S-layer (surface layer) is a cell surface protein layer found in many different bacteria and in some archaea, where it serves as the cell wall. All S-layers are made up of a two-dimensional array of proteins and have a crystalline appearance, the symmetry of which differs between species.
An S-layer (surface layer) is a part of the cell envelope found in almost all archaea, as well as in many types of bacteria. [1] [2] The S-layers of both archaea and bacteria consists of a monomolecular layer composed of only one (or, in a few cases, two) identical proteins or glycoproteins. [3]
The outer red layer in this diagram is the capsule, which is distinct from the cell envelope. This bacterium is gram-positive, as its cell envelope comprises a single cell membrane (orange) and a thick peptidoglycan-containing cell wall (purple). The bacterial capsule is a large structure common to many bacteria. [1]
Another highly organized, but separate structure is an S-layer. S-layers are structures that integrate themselves into the cell wall and are composed of glycoproteins, these layers can offer the cell rigidity and protection. [6] Because a slime layer is loose and flowing, it does not aide the cell in its rigidity.
Instead, the extracellular forms of these Gram-negative bacteria maintain their structural integrity by relying on a layer of disulfide bond cross-linked cysteine-rich proteins, which is located between cytoplasmic membrane and outer membrane in a manner analogous to the peptidoglycan layer in other Gram-negative bacteria. [4]
Lysozyme is more effective in acting against gram-positive bacteria, in which the peptidoglycan cell wall is exposed, than against gram-negative bacteria, which have an outer layer of LPS covering the peptidoglycan layer. [31] Several bacterial peptidoglycan modifications can result in resistance to degradation by lysozyme.