Biofilm Formation

    Cards (9)

    • the Wsp system (TCS) controls biofilm formation in P. aeruginosa with many components
      • WspA -> sensor that detects growth on solid surfaces (mechanosensing)
      • Wsp B/D -> adaptor proteins
      • WspE -> HK
      • WspR -> RR
      • WspF -> demethylase (RR), sensitizes to surface contact
      • WspC -> methyltransferase, desensitize to surface contact
    • WspR has 2 domains
      • RR/receiver domain that gets phosphorylated to turn on the ->
      • diguanylate cyclase (DGC) enzymatic domain that makes c-di-GMP which allosterically binds and inhibits FleQ which is a positive regulator for flagella and negative for biofilm
      • SO if c-di-GMP inhibits FleQ then flagella is inhibited and biofilm formation is activated
    • the diguanylate cyclase domain of WspR have 5 conserved amino acids (GGDEF) in its active site
    • WspR uses 2 GTP molecules to make c-di-GMP which forms 2 pyrophosphate molecules
    • the WspR protein binds 1 GTP which homodimerizes upon phosphorylation to make c-di-GMP
    • the 2 mechanisms to inactivate DGC domain on WspR
      • phosphorylation dependent
      • phosphorylation independent
    • mechanism to inactivate DGC domain on WspR
      • phosphorylation dependent -> bacteria can't sense a surface -> WspR dephosphorylates by phosphatase -> WspR becomes monomeric subunit and returns to planktonic lifestyle
      • occurs spontaneously OR by phosphatase
    • mechanism to inactivate DGC domain on WspR
      • phosphorylation independent -> c-di-GMP homodimerizes (1mM) -> homodimeric c-di-GMP allosterically binds to DGC domain of WspR which forces it into inactive conformation
      • unregulated c-di-GMP production causes GTP depletion (toxic)
      • an intrinsic property of GMP is that high levels of GMP can homodimerize
      • this is a negative feedback loop and gives bacteria the opportunity to exit biofilm state
    • FleQ TF can negatively affect biofilm formation and positively affect motility by having a consensus sequence specific for FleQ to bind and depending where it is on the gene it can enhance/inhibit transcription of genes