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The bacterial cell wall differs from that of all other organisms by the presence of peptidoglycan which is located immediately outside of the cell membrane. Peptidoglycan is made up of a polysaccharide backbone consisting of alternating N-Acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) residues in equal amounts.
This figure depicts fimbriae adhesion. In this process the fimbriae of a bacterial cell (right) adhere to specific proteins, called receptors, found on the outer membrane of a host cell (left). They do this by a specific interaction between the receptors of the host cell and the perfectly matched adhesions found on the bacteria's fimbriae.
The bacterial cells are ~ 0.5 μm wide [126] Most bacteria have a single circular chromosome that can range in size from only 160,000 base pairs in the endosymbiotic bacteria Carsonella ruddii, [127] to 12,200,000 base pairs (12.2 Mbp) in the soil-dwelling bacteria Sorangium cellulosum. [128]
Spiral bacteria are another major bacterial cell morphology. [2] [30] [31] [32] Spiral bacteria can be sub-classified as spirilla, spirochetes, or vibrios based on the number of twists per cell, cell thickness, cell flexibility, and motility. [33] Bacteria are known to evolve specific traits to survive in their ideal environment. [34]
The cell envelopes of the bacterial class of mollicutes do not have a cell wall. [5] The main pathogenic bacteria in this class are mycoplasma and ureaplasma. [5] L-form bacteria are strains bacteria that lack cell walls derived from bacteria that normally possess cell walls. [6]
The bacterial capsule is a large structure common to many bacteria. [1] It is a polysaccharide layer that lies outside the cell envelope, and is thus deemed part of the outer envelope of a bacterial cell. It is a well-organized layer, not easily washed off, and it can be the cause of various diseases.
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.
When studied, many misshapen bacteria were found to have mutations linked to development of a cell envelope. [40] The cytoskeleton was once thought to be a feature only of eukaryotic cells, but homologues to all the major proteins of the eukaryotic cytoskeleton have been found in prokaryotes. [41]