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