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Adhesin

Adhesin_Dr
PDB 1ut1 EBI.jpg
drae adhesin from escherichia coli
Identifiers
Symbol Adhesin_Dr
Pfam PF04619
Pfam clan CL0204
InterPro IPR006713

Adhesins are cell-surface components or appendages of bacteria that facilitate adhesion or adherence to other cells or to surfaces, usually the host they are infecting or living in. Adhesins are a type of virulence factor.

Adherence is an essential step in bacterial pathogenesis or infection, required for colonizing a new host.

Bacteria are typically found attached to and living in close association with surfaces. During the bacterial lifespan, a bacterium is subjected to frequent shear-forces. In the crudest sense, bacterial adhesins serve as anchors allowing bacteria to overcome these environmental shear forces, thus remaining in their desired environment. However, bacterial adhesins do not serve as a sort of universal bacterial Velcro. Rather, they act as specific surface recognition molecules, allowing the targeting of a particular bacterium to a particular surface such as root tissue in plants, lacrimal duct tissues in mammals, or even tooth enamel.

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. In gram-positive bacteria, a protein or polysaccharide surface layer serves as the specific adhesin. To effectively achieve adherence to host surfaces, many bacteria produce multiple adherence factors called adhesins.

Bacterial adhesins provide species and tissue tropism. Adhesins are expressed by both pathogenic bacteria and saprophytic bacteria. This prevalence marks them as key microbial virulence factors in addition to a bacterium’s ability to produce toxins and resist the immune defenses of the host.

Through the mechanisms of evolution, different species of bacteria have developed different solutions to the problem of attaching receptor specific proteins to the bacteria surface. Today many different types and subclasses of bacterial adhesins may be observed in the literature.


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