adhesins

Adhesins are a diverse set of surface-exposed proteins and glycoproteins that mediate attachment of microorganisms to host cells, tissues, or extracellular matrix. They enable initial colonization, promote persistence and biofilm formation, and are key determinants of virulence in many bacteria, fungi, and parasites.

Adhesins are located on the cell surface, either as part of pili (fimbriae) with the adhesin at the tip, or as afimbrial surface proteins. In Gram-positive bacteria, many adhesins are MSCRAMMs anchored to the cell wall by sortase enzymes. In Gram-negative bacteria, adhesins include fimbrial tip proteins, autotransporters, and outer membrane receptors.

Well-known bacterial adhesins include FimH of uropathogenic E. coli, which binds mannose residues; PapG, a P pilus adhesin; Staphylococcus aureus clumping factor A and fibronectin-binding proteins; Streptococcus pyogenes M protein; Listeria monocytogenes internalin A, which interacts with E-cadherin; Helicobacter pylori BabA, which binds Lewis b antigens.

Role in disease and applications: Adhesins influence tissue tropism and host range, are targets for vaccines and therapeutics, and are involved in biofilm development. Inhibitors of adhesin–receptor interactions, such as FimH antagonists (mannosides), are being explored as anti-adhesive therapies.