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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.
FimH is a bacterial adhesin that helps bacteria such as Escherichia coli to bind to host cells and their receptors (here: the human proteins CD48 and TLR4, or mannose residues). [ 4 ] Most fimbria of gram-negative bacteria function as adhesins, but in many cases it is a minor subunit protein at the tip of the fimbriae that is the actual adhesin.
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.
A fimbria (plural fimbriae also known as a pilus, plural pili) is a short, thin, hair-like filament found on the surface of bacteria. Fimbriae are formed of a protein called pilin and are responsible for the attachment of bacteria to specific receptors on human cells (cell adhesion).
Bacteria produce various adhesins including lipoteichoic acid, trimeric autotransporter adhesins and a wide variety of other surface proteins to attach to host tissue. Capsules, made of carbohydrate, form part of the outer structure of many bacterial cells including Neisseria meningitidis.
The human body carries endogenous stores on LPS. [34] The epithelial surfaces are colonized by a complex microbial flora (including gram-negative bacteria), which outnumber human cells by a factor of 10 to 1. Gram-negative bacterial will shed endotoxins.
While some receptors are cell-surface proteins, others are found inside cells. For example, estrogen is a hydrophobic molecule that can pass through the lipid bilayer of the membranes . As part of the endocrine system , intracellular estrogen receptors from a variety of cell types can be activated by estrogen produced in the ovaries .
For example: proteins, enzymes or toxins (such as cholera toxin in pathogenic bacteria e.g. Vibrio cholerae) from across the interior (cytoplasm or cytosol) of a bacterial cell to its exterior. Secretion is a very important mechanism in bacterial functioning and operation in their natural surrounding environment for adaptation and survival.