M14- Biochemistry of plaque

Question 1

what does dental plaque effect?

Answer 1

• effects teeth
• effects periodontal tissues
• effects itself

Question 2

what are bacterial cells constantly doing?

Answer 2

• metabolizing
• dividing
• dying

Question 3

what does plaque release?

Answer 3

• metabolic and waste products
• cell components
• can damage both teeth and promote periodontal disease

Question 4

Describe plaque as a community.

Answer 4

– Bacteria compete to colonise & proliferate in different niches
– Strategies have developed through selection
– Selective pressures will alter as plaque develops

Question 5

Describe synergistic interactions (beneficial).

Answer 5

• 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

Question 6

what is Quorum sensing (cell to cell communication)?

Answer 6

Co-ordina)on of gene expression & developmental pathways

triggered by sensing the environment including behaviour/amount of other bacteria

Question 7

what are the 3 main carbon sources for carbohydrate metabolism?

Answer 7

sucrose, lactose and starch

Question 8

What are the 3 types of fermentation?

Answer 8

• Homofermentation
– bacteria produce one fermentation product
• Heterofermentation
– bacteria produce more than one fermentation product
• Homo & Heterofermentation
– switch according to growth conditions

Question 9

what is used as nutrient source for nitrogen metabolism?

Answer 9

salivary proteins/ glycoproteins

Question 10

what does ammonia production do?

Answer 10

counters development of low pH

Question 11

what does regular carbohydrate intake result in?

Answer 11

– Reduction in pH
– Favours S. mutans &
Lactobacillus

Question 12

what is an extracellular end product?

Answer 12

fusobacteria

Question 13

why is type of carbohydrate important?

Answer 13

– Sucrose promotes EPS

– Lactose can disturb some interactions in vitro

Question 14

What is involved in antagonistic interactions (damage competitors)?

Answer 14

– Competition for substrates
– Metabolic products
• Acid production by Streptococci
– Bacteriocins

Question 15

what is bacteriocin?

Answer 15

a substance released by one bacteria that kills another usually by inducing a metabolic block

Question 16

what is the substance normally released?

Answer 16

• Substance normally a protein

* Normally active against same species can extend to closely related species

Question 17

what substance is active against against various streptococci species?

Answer 17

Mutacins

Question 18

Name the toxic products of plaque bacteria .

Answer 18

•  fermentation and glycolysis products: organic acids
alcohols
•  nitrogenousproducts:
NH3
•  sulphurousproducts:
H2S
•  toxicsubstances:
endotoxins
bacterial enzyme toxins

Question 19

what is the product of degradation of sulphur-containing amino acids?

Answer 19

hydrogen sulphide

Question 20

what are toxic substances?

Answer 20

Endotoxin; lipopolysaccharides (LPS) – outer membranes of Gram -ve cell walls (PG)

Question 21

when are endotoxins released?

Answer 21

released on death of bacteria

Question 22

what are the biological effects of endotoxins?

Answer 22

• fever
• raise capillary permeability
• elicit inflammation

Question 23

What plaque bacteria release endotoxins?

Answer 23

Veillonella, Bacteriodes, Porphyromonas, Prevotella etc

Question 24

what is endo-toxin induced inflammation a result of?

Answer 24

antigenic properties

Question 25

Name enzymes that break down human tissues and cells.

Answer 25

– general proteinases
– specific proteinases, (collagenases etc)
– polysaccharidases, (hyaluronidases etc)
– lipases

Question 26

what produces collagenase?

Answer 26

bacteriodes ,prevotella and porphyromonas

Question 27

Describe localisation (interactions determine biofilm architecture).

Answer 27

• 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