Short definitions of terms used across adhesins.com. Terms link back to concepts covered in the articles.
- Adhesin
- A surface molecule, usually a protein, that allows a microorganism to bind a specific receptor on a host cell, extracellular matrix or surface.
- Afimbrial (non-fimbrial) adhesin
- An adhesin that is anchored directly in the bacterial outer membrane or cell wall rather than displayed on a pilus, for example intimin or many autotransporter adhesins.
- Als proteins
- A family of cell-surface glycoproteins of the yeast Candida albicans that mediate adhesion to host cells and contribute to biofilm formation.
- Autotransporter
- A protein exported by the type V secretion system that carries its own outer-membrane translocation domain; many autotransporters act as adhesins.
- BabA / SabA
- Helicobacter pylori adhesins that bind fucosylated (Lewis b) and sialylated (sialyl-Lewis x) glycans on gastric epithelium.
- Biofilm
- A structured community of microorganisms attached to a surface and embedded in a self-produced extracellular matrix. Biofilm cells are typically far more tolerant of antibiotics than planktonic cells.
- Catch bond
- A receptor-ligand bond that becomes stronger, rather than weaker, when tensile force is applied. FimH-mannose binding is a well-studied example that helps bacteria resist flow.
- Chaperone-usher pathway
- The assembly route for many Gram-negative pili (such as type 1 and P pili): a periplasmic chaperone stabilises pilin subunits and an outer-membrane usher assembles them into a fibre.
- Clumping factor A (ClfA)
- A Staphylococcus aureus MSCRAMM that binds fibrinogen; it has been studied as a vaccine and antibody target.
- Curli
- Functional amyloid fibres made mainly of the CsgA protein by E. coli and Salmonella; important for biofilm matrix and adhesion.
- Extracellular polymeric substances (EPS)
- The matrix of polysaccharides, proteins, lipids and extracellular DNA that holds a biofilm together.
- Fibronectin-binding proteins (FnBPs)
- Staphylococcal surface proteins that bind fibronectin and can promote uptake of bacteria into host cells via integrins.
- FimH
- The mannose-binding adhesin at the tip of type 1 fimbriae of E. coli; central to bladder colonisation by uropathogenic strains.
- Fimbriae
- Short, thin, hair-like protein fibres on the bacterial surface that usually mediate adhesion. Often used interchangeably with "pili".
- Intimin / Tir
- Intimin is an outer-membrane adhesin of enteropathogenic and enterohaemorrhagic E. coli; it binds Tir, a receptor that the bacterium itself injects into the host cell membrane.
- Invasin
- A Yersinia outer-membrane protein that binds host beta-1 integrins and triggers uptake of the bacterium into host cells.
- Lectin
- A protein that binds specific carbohydrates. Many adhesins, including FimH and PapG, are lectins.
- LPXTG motif / sortase
- A C-terminal sorting signal on many Gram-positive surface proteins. The enzyme sortase A cleaves it and covalently links the protein to the cell-wall peptidoglycan.
- Mannoside
- A synthetic or natural compound containing mannose. Designed mannosides that block FimH are studied as anti-adhesion agents.
- MSCRAMM
- Microbial Surface Components Recognizing Adhesive Matrix Molecules: cell-wall-anchored proteins of staphylococci and other Gram-positive bacteria that bind host matrix proteins such as fibrinogen, fibronectin and collagen.
- P pili / PapG
- Pili of uropathogenic E. coli associated with kidney infection (pyelonephritis); the PapG tip adhesin binds Gal-alpha(1-4)-Gal glycolipids.
- Phase variation
- Reversible on/off switching of gene expression, for example of fimbrial genes, that produces mixed bacterial populations and can help evade immunity.
- Pilicide
- A small molecule that interferes with pilus assembly, typically by targeting the chaperone-usher pathway.
- Pilin
- The protein subunit that polymerises to form the shaft of a pilus.
- Quorum sensing
- Cell-density-dependent signalling between bacteria using secreted signal molecules; it regulates biofilm maturation and many virulence genes.
- Sortase
- A transpeptidase enzyme of Gram-positive bacteria that anchors surface proteins, including many adhesins and pili, to the cell wall.
- Tissue tropism
- The preference of a microorganism for particular tissues or cell types, often determined by which host receptors its adhesins recognise.
- Type IV pili
- Retractable pili found in many Gram-negative bacteria (for example Neisseria and Pseudomonas) that mediate adhesion, twitching motility and DNA uptake.
- Uroplakins
- Glycoproteins on the surface of bladder umbrella cells; mannosylated uroplakin Ia is a receptor for FimH.
- UPEC
- Uropathogenic Escherichia coli, the most common cause of urinary tract infections; it relies on type 1 and P pili among other factors.