integument formation - biofilms Flashcards
What is required for the stabilisation of plaque?
synthesis of a bacterial extracellular polysaccharide “matrix” (EPS)
explain these results
no bacterial aggregation on gucose
bacterial aggregation shown on sucrose
- bacteria aggregate when coming into contact with dextran (glucan)
- the bacteria begin to lay down the extracellular polysaccharide matrix
What converts sucrose to glucan?
enzymes : glucosyltransferases (Gtf’s)
what makes glucans soluble
contain a higher proportion of alpha 1-6 linked glucans
what makes glucans insoluble?
contain predominantly alpha 1-3 linked glucans
which glucans are involved in establishing an EPS matrix
insoluble glucans
therefore they are virulence factors
give examples of S.mutants glucotransferases and what glucans they form
- GtfB:
- insoluble glucan α1,3 linked glucan
- Very important for stabilisation of the EPS matrix
- GtfC:
- mixture of soluble α1,6 linked glucan & insoluble
- GtfD: soluble glucans
- Not involved in establishing EPS matrix
- Not a virulence factor
what is the significance of the C-terminal repeat motifs in GtfC
- able to bind to lysosyme and amylase in the saliva
- allowing Gtf to bind to the pellicle
- enzymes can be sequestered to the tooth surfaces through the pellicle
- drives production of the EPS matrix
What changes to the properties of Gtf occurs when binding to the pellicle?
Gtf becomes hyperactive
- more capable to form crosslinkings that lead to the stabilisation of the EPS matrix
- more stable at a wider pH range
- can more optimally convert sucrose into glucans
- therefore increase in insoluble glucan synthesis
- most establishment of EPS matrix
what does a signal peptide on Gtf’s show?
which Gtf’s contain them
the enzyme is secreted by the bacteria into the oral environment
both GtfC and GtfB have a signal peptide
What is the significance of the C-terminal repeat motifs in GtfB?
- It can form bacterial binding sites
- allows transfer of Gtf activity from S.mutants to other bacterial species
- increased synthesis of EPS matrix
how does the EPS matrix lead to a drop in oral pH??
What effect does this drop in oral pH have on Gtf and the EPS matrix?
- EPS matrix is able to be metabolised to acid like sugars
- therefore drop in pH
- leads to
- upregulation of some Gtf activity
- upregulation of synthesis of Gtf’s by s.mutants
- increase in matrix production
What other bacteria can further colonise the EPS and how do they effect health?
- acidogenic or aciduric bacteria can colonise the biofilm
- further establishment of diversity
- increased caries risk
- P.gingivalis
- increased gingivitis risk
what are EPS-microcolonies?
- acidic niches in the biofilm
- areas that retain acid for prolonged periods of time
- high bacterial colonisation
- where enamel erosion will occur
What evidence of is there to show the importance of Gtf’s as virulence factors
Genetically modified S.mutants lacking genes encoding glucosyl transferases – GtfB/C
- did not form EPS-microcolony complexes
- can be readily neutralised
- matrix was not crosslinked
- less complex structures
- fail to generate acid environments
- can be readily neutralised
