Lecture 15 Flashcards
Why are biofilms resistant to cell loss?
Because cells are tightly stuck together, shearing the force of blood, urine or other fluids that often dislodge other cells.
Why are biofilms resistant to antibiotics?
Because the cells in the interior of the biofilm are inaccessible to antibiotics and/or are metabolically dormant
What are the steps to biofilm formation
- Attachment
- Colonisation
- Structuring
- Detachment
How do Fibronectin binding proteins allow attachment of S.aureus to medical implants?
Fibronectin in blood coats the surface of medical implants. FnBP (fibronectin binding protein) on the surface of S.aureus mediates binding of bacteria to fibronectin. Attachment resembles bridging mechanism of adherance to host cells.
What is the role of Polysaccharide Intercellular Adhesin (PIA) in maturation of biofilms?
PIA is a +vely charged polymer compromised of modified N-acetylglucosamide. PIA forms an extracellular matrix that causes the S.aureus cells in the biofilm to stick together.
What is the role of phenol soluble modulins (PSMs) in structuring of biofilms?
PSMs promote structuring and detachement of biofilms.
What is the purpose of ‘structuring’ of biofilms?
Structuring is the loss of regions in the biofilm, resulting in the formation of fluid filled channels that allow delivery of nutrients that allow delivery of nutrients into deeper layers of the biofilm.
How are PSMs regulated?
PSM expression is under the control of quorum sensing. PSMs are only expressed once the biofilms are mature.
RNAIII is the precursor to S.aureus toxins and PSMs. How is this controlled?
The ribosome binds to the shine-delgarno sequence of the RNAIII at high bacterial density to produce PSMs and toxins.
At low bacterial concentrations, the shine delgarno sequence is not available and the toxins/PSMs are not produced.
