M14- Biochemistry of plaque Flashcards
what does dental plaque effect?
- effects teeth
- effects periodontal tissues
- effects itself
what are bacterial cells constantly doing?
- metabolizing
- dividing
- dying
what does plaque release?
- metabolic and waste products
- cell components
- can damage both teeth and promote periodontal disease
Describe plaque as a community.
– Bacteria compete to colonise & proliferate in different niches
– Strategies have developed through selection
– Selective pressures will alter as plaque develops
Describe synergistic interactions (beneficial).
- Enzymes secreted or released upon lysis can benefit more than one species
- Metabolic products can be beneficial to other species.
- Adhesion to other species or cell products (glucans)
- Cell to cell signaling (Quorum sensing & coordinated behaviour)
- Gene transfer, acquisition of useful genes & increased genetic variation
what is Quorum sensing (cell to cell communication)?
Co-ordina)on of gene expression & developmental pathways
triggered by sensing the environment including behaviour/amount of other bacteria
what are the 3 main carbon sources for carbohydrate metabolism?
sucrose, lactose and starch
What are the 3 types of fermentation?
• Homofermentation
– bacteria produce one fermentation product
• Heterofermentation
– bacteria produce more than one fermentation product
• Homo & Heterofermentation
– switch according to growth conditions
what is used as nutrient source for nitrogen metabolism?
salivary proteins/ glycoproteins
what does ammonia production do?
counters development of low pH
what does regular carbohydrate intake result in?
– Reduction in pH
– Favours S. mutans &
Lactobacillus
what is an extracellular end product?
fusobacteria
why is type of carbohydrate important?
– Sucrose promotes EPS
– Lactose can disturb some interactions in vitro
What is involved in antagonistic interactions (damage competitors)?
– Competition for substrates
– Metabolic products
• Acid production by Streptococci
– Bacteriocins
what is bacteriocin?
a substance released by one bacteria that kills another usually by inducing a metabolic block
what is the substance normally released?
- Substance normally a protein
* Normally active against same species can extend to closely related species
what substance is active against against various streptococci species?
Mutacins
Name the toxic products of plaque bacteria .
• fermentation and glycolysis products: organic acids alcohols • nitrogenousproducts: NH3 • sulphurousproducts: H2S • toxicsubstances: endotoxins bacterial enzyme toxins
what is the product of degradation of sulphur-containing amino acids?
hydrogen sulphide
what are toxic substances?
Endotoxin; lipopolysaccharides (LPS) – outer membranes of Gram -ve cell walls (PG)
when are endotoxins released?
released on death of bacteria
what are the biological effects of endotoxins?
- fever
- raise capillary permeability
- elicit inflammation
What plaque bacteria release endotoxins?
Veillonella, Bacteriodes, Porphyromonas, Prevotella etc
what is endo-toxin induced inflammation a result of?
antigenic properties
Name enzymes that break down human tissues and cells.
– general proteinases
– specific proteinases, (collagenases etc)
– polysaccharidases, (hyaluronidases etc)
– lipases
what produces collagenase?
bacteriodes ,prevotella and porphyromonas
Describe localisation (interactions determine biofilm architecture).
• Co-aggregation or co-adhesion
• Extracellular polymers, acid & bacteriocins localised
• Plaque-tooth interface
– bacterial breakdown is occurring
– and diffusion of NH3 out into saliva is limited
– high local concentrations of ammonia may occur
– Important for asaccharolytic organism of periodontal pocket
