intro to dental plaque Flashcards
(41 cards)
What is dental plaque?
community of microorganisms found on tooth surface as a biofilm embedded in matrix of polymers of salivary bacterial origin
Where is dental plaque found?
Pits and fissures
Exopolymer
deposited outside the cell e.g. plaque
-When attached to surface, they grow naturally and have diff phenotypes
What is order of biofilm formation?
- conditioning film
- transport of microbes
- reversible phase
- irreversible phase
- secondary colonisation
- growth and matrix synthesis
- detachment
conditioning film
-Determines organism able to colonise
-forms rapidly up to 1 um thick
What is condtioning film made up of
Saliva, GCF and microbes
How is biofilm produced
-produced by host/bacterial e.g. amylase, immunoglobulins, proline rich peptides, mucins, agglutinins
How does microbial transport happen
passive
Reversible attachment
Microbes held in place by Weak, long range, van der Waals forces
Step 4-irresversoble
-primary colonisers have specific binding
-step 5- secondary colonisers only designed to bind onto primary colonisers
-with adhesin-receptor interactions
E.g. streptococcus spp release adhesin- antigen i/II which attached to receptors on cell surface salivary agglutinin
How is co-adhesion used
Some early inhabitants are streptocci-have anti-inflammatory properties, reduce blood pressure
-favourable to us
-as biofilm matures, it increases in biodiversity
-bridging organisms- can link to most types of cells (usually only specific)
Biofilm maturation
Bacteria are in close proximity and start to interact with each other by excreting cell signalling molecules, break down substrates, modify environment to make it more favourable to them
e.g. peptides (gram pos)
-autoinducer-2 (gram neg)
Metabolic interactions in biofilm maturation
-Within mature biofilm, there are many complex metabolic reactions occurring between microbes e.g. organism depend on each other for nutrients
-interaction with community of bacteria to work together and sequentially degrade sugar components
-metabolism occurs sequentially, require collaboration, takes lot of metabolic effort
-means microbial community needs to be stable as they depend on each other
E.g. glucose breakdown
-streptococcus uses glucose, breaks it down to lactic acid. Lactic acid is taken up by villanella which use it as nutrients for their growth and produce acetate and propionate as waste product.
So breakdown of a strong acid (needed for mineralisation of teeth) into weaker acid
What do bacteria metabolise
In order to survive in habitat, bacteria needs to attach to surface and grow. They metabolise glycoproteins that have protein backbone with short chain sugars
-protein backbone–protease–peptides–peptidase–amino acids–CO2 and NH3 (deamination)
another e.g. of polymer degrading bacteria
oligosaccharides–monosaccharides–fatty and hydroxy acids alcohols–H2, CO2, CH4, H2S
What is biofilm matrix function?
-protection from extreme environment
-nutritional reserve
-stabilises biofilm (structural support)
-interacts with molecules (retains enzymes, ions)
-water retention
what is plaque/biofilm matrix
-polymers derived from host and bacteria
-30% plaque volume
-bacterial polysaccharides e.g. gluten, mutan, fructan
-bacterial polymers e.g. eDNA
n sucrose broken down to (glucan)n + n-fructose by glucosyltransferase
n sucrose broken down to (fructan)n + n-glucose by fructosyltransferase
beneficial interactions in microbial communities in biofilm maturation
-food chain/food web
-eznyme complementation
-cell-cell signalling
-inhibitor neutralisation
antagonistic interactions in microbial communities in biofilm maturation
-bacteriocins
-hydrogen peroxide
-organic acids
-low pH
-nutrient compeittion
How typical microbial community functions with diff types of interaction in matrix
-waste products of one organisms is food for another
-environment responsible for providing genes to them which can favour antibiotic resistant genes
-microorgs more virulent as community than as individual
-arrows show microbes able to stop things coming in form outside and prevent things from inside getting out
-spacially and functionally organised, work together well
How does detachment happen?
-If environment becomes negative e.g. resources depleted, organism produce protease that allow them to detach from matrix and colonise elsewhere
early stages of dental biofilm formation
-limited no. of species
-mainly streptococci
-mainly aerobic/facultatively anaerobic
late stages of biofilm formation
-diverse community
-100-300 species
-obligateuly anaerobes
-cell-cell associations
-microbial interactions
