06_adhesion

crutial for successful establishment of infection by bacterial pathogens & later colonisation of tissue, intracellular multiplication, dessemination to other tissue and/or persistence

• long fibrillary organelles: fimbraie/pili

• cell wall associated molecules: capsules, flagella

  
  

pili: thin, protein tubes orginiating from cytoplasmic membrane (primarily in virtually all Gram-negative bacteria)

-> constantly losing and reforming w. switch of adhesive tips in order to adhere to different types of cells and evade immune defenses

adherance to receptors of target host cells by adhesive tip structure of shafts

-> depolymerisation and enabling adhesions in bacterial cell well for more intimate contact

-> colonise and resists flushing out by body

• Neisseria gonorrhoeae

• Escherichia coli

• Vibrio cholerae

• Pseudomonas aeruginosa

• firm operon encodes type 1 pili

• pap operon encodes P-/Pap pili -> interaction w. P-blood group antigen

-> can’t get cleared by bladder easily

-> both heteropolymeric pili

hydrophobic core -> may provide extreme mechanical strength

allows attachment (of other bacteria) and enables twitching motility (crawling and walking)

-> gliding motility along a solid surface (host cell)

-> dragging motility through extension and retraction of pili

e. g.: N. gonorrhoeae, Neisseria meningitidis, V. colerae, P. aeuruginosa

surface proteins in cell wall of various bacteria binding to specific receptor molecules on host cell surface

-> intimidate adhesion (1 or more) in order to colonise and resist physical removal

microbial surface components recognising adhesive matrix proteins

• two adjacent IgG-folded domains

• mediation of attachment to components of host ECM (collagen, fibrinogen, fibrinonectin Fn)

  • collagen binding protein

  • Protein A (binds IgG)

  • clumping factor (binds fibrinogen)

  • peptidoglycan

  • capsule

  • fibronectin-binding protein

• molecular binding mechanisms depending on adhesion types

  • dock lock latch: latch to attach

  • collagen hug: looping around collagen

  • tandem beta-zipper: beta-sheets

production of capuslar polysaccharide matrix or glycocalyx to form a biofilm on host tissue

1. reversible attachment

2. irreversible absorption

3. cell proliferation and production of ECM

4. biofilm maturation

5. biofilm detachment

6. spread of microbial cells

• H7 flagellum in E. coli (mediates binding to intestinal epithelial cells)

• Pseudomonas aeruginosa (binding to mucus)

• clostridioides difficile (for adherence and colonisation of intestinal epithelium during infection)

EPEC - strain example: E. coli O157

• utilisation of type 3 secretion system (T3SS) to inject effector protein into intestinal epithelial cells -> formation of pedestal (characteristic lumps at receptos under microscope)

• causing acute and chronic pediatric diarrhea

• formation of attaching and effacing (A/E) lesions in intestinal epithelium -> mediated by genes at locus of enterocyte effacement (LEE) => encode adhesion intimin, T3SS, six effectors and interaction btw. Tir and intimin as anchor for bacterium to host membrane

induction of host cells to display more receptors on their surface for H. pylori adhesins

=> drill like, tubal structure into host cell

-> causes chronic gastritis, peptic ulcers and in the long run gastric cancer

• adherance to galactose residues of glycolipids on respiratory tract by filamentous hemagglutinin

• pertussis toxin: subunit remains baound to bacterial cell wall, others bind to glycolipids on membrane of epithelial cells of respiratory tract

• adhesin pertactin: further enbabling bacterium to adhere

production of adhesin Opa -> enables more intimate contact with host cell after first adhesion

-> multiple alleles for Opa protein adhesins => adhestion to a variety of host cell types possible

• Borellia burgdorferi

• Treponema pallidum

• Streptococcus pyogenes