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Archaea and bacteria have generally similar cell structure, but cell composition and organization set the archaea apart. Like bacteria, archaea lack interior membranes and organelles . [ 68 ] Like bacteria, the cell membranes of archaea are usually bounded by a cell wall and they swim using one or more flagella . [ 119 ]
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 cell wall of bacteria is also distinct from that of Archaea, which do not contain peptidoglycan. The cell wall is essential to the survival of many bacteria, although L-form bacteria can be produced in the laboratory that lack a cell wall. [ 38 ]
The different peptidoglycan types of bacterial cell walls and their taxonomic implications have been described. [11] Archaea (domain Archaea) [12] do not contain peptidoglycan (murein). [13] Some Archaea contain pseudopeptidoglycan (pseudomurein, see below). [14]
Pseudopeptidoglycan (also known as pseudomurein; [2] PPG hereafter) is a major cell wall component of some Archaea that differs from bacterial peptidoglycan in chemical structure, but resembles bacterial peptidoglycan in function and physical structure. Pseudopeptidoglycan, in general, is only present in a few methanogenic archaea.
The three-domain system adds a level of classification (the domains) "above" the kingdoms present in the previously used five- or six-kingdom systems.This classification system recognizes the fundamental divide between the two prokaryotic groups, insofar as Archaea appear to be more closely related to eukaryotes than they are to other prokaryotes – bacteria-like organisms with no cell nucleus.
Around the outside of the cell membrane is the cell wall. Bacterial cell walls are made of peptidoglycan (also called murein), which is made from polysaccharide chains cross-linked by peptides containing D-amino acids. [75] Bacterial cell walls are different from the cell walls of plants and fungi, which are made of cellulose and chitin ...