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Stage 2 Microbiology for dentists > MFD 22 > Flashcards

MFD 22 Flashcards

Aim • To describe the key components and functions of the extracellular matrix of dental plaque. Content • Exopolysaccharide production. • Fructans • Glucans • Glucan binding proteins • Proteins and Nucleic acids. • Plaque fluid and enamel dissolution.

1
Q

1) What macromolecules form the basic structure of dental plaque?
2) What Small molecules may be trapped within the matrix (ie the ‘plaque fluid’): ?

A

1) polysaccharides, proteins, nucleic acids

2) nutrients, metals, signalling molecules

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2
Q

What is responsible for the ‘crystalline’ colony appearance on sucrose-containing agar ?

A

Exopolysaccharides – glucans and fructans

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3
Q

What are the 2 types of exopolysaccharides?

2) what interesting about them?
3) Where does the energy come from?

A

1) glucans and fructans
2) they are formed outside the cell, synthetic reactions never occur outside the cell usually as require energy
3) sucrose has a high energy

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4
Q

are the exopolysaccharides soluble or insoluble?

2) What structure do they have?

A

1) either

2) varies, but very complex

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5
Q

What enzyme is used to make glucans?

A

Glucosyltransferase (GTF)

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6
Q

What enzyme is used to make fructans?

A

Fructosyltransferase (FTF)

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7
Q

watch a youtube video on numbering carbons in sugar

A

go over reactions in glucan synthesis

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8
Q

What is the function of Fructan Polymers: Inulins (β-2,1 bond type, 95%, beta-2,6 bond type 5%) ?
2) What synthesises it?

A

long term storage carbohydrate instead of starch
2) Only synthesised by Strep. mutans &
some strains of Strep. salivarius

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9
Q

Which is soluble and which is insoluble:

1) Fructan Polymers: Inulins (β-2,1 bond type, 95%, beta-2,6 bond type 5%)
2) Fructan Polymers: Levans (β-2,6 bond type)

A

1) insoluble

2) soluble

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10
Q

Fructan Polymers: Levans (β-2,6 bond type)

1) Is it made by strep. sanguinis
2) is it made by actinomyces
3) is it made by strep. mutans
4) FUNCTION:

A

1) yes
2) yes
3) no
4) adheres bacteria together in biofilm, but 1,3-linked, making it insoluble

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11
Q

What are the 2 types of fructan?

A

1) Levans (β-2,6 bond type) (possible there is a 1,3-linked form that is insoluble)
2) Inulins (β-2,1 bond type)

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12
Q

What is the name of the insoluble glucan polymer?

A
  • water insoluble (mutan)

* core is α-1,3 linked

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13
Q

What the soluble glucan polymers?

A
  • water soluble (dextran)
  • core is α-1,6 linked
  • many variations!
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14
Q

What is the only substrate for glucan synthesis?

2) Why?

A

1) sucrose
2) releases a high amount of free energy when bond broken, Free energy in the glycosidic bond of sucrose is 29 kj/mol (equiv. to phosphorylated precursors eg UDP- glucose) ,
energy used to make glycosidic bond in maltose which has a lower kj/mol

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15
Q

What is the common name given to a linear chain fo fructose joined by beta2,1 links?
2) What type of link is the cross links?

A

1) Inulins

2) beta 2,6 glycosidic bonds

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16
Q

What is the name of a linear polymer of fructose with beta 2,6 links?
2) Why is it called this?

A

levans

2) rotates polarised to the left

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17
Q

Describe the polymer structure of mutans:

A

In some bacteria almost entirely alpha 1,3, linear. with a few alpha 1,6 branches.
In other strains, 85%-90% is alpha 1,3 and the rest is alpha 1,6.

18
Q

Which exopolysaccharide makes up 70% of plaque?

A

mutans

19
Q

What makes glucose more cariogenic than sucrose?

A

glucose can be used to make mutans, which is insoluble so despite being more slowly produced and not forming as much acid per monomer, it has a lower turnover so sticks the bacteria to the teeth better.

20
Q

1) What glycosidic bond present in dextrans?

2) describe the variation in structure from typical dextras to the one formed by strep sobrinus:

A

1) alpha- 1,6
2) • side branch is short compared with the backbone
• there is a side branch for about every 15 backbone residues. The side branch is an alpha-1,3 glycosidic bond.

21
Q

Why is dextrans called dextrans?

A

rotates polarised light to the right

22
Q

What adds to the complexity of structure of exopolysaccharides?

A

as they are synthesized in the external environment, the rate of enzymes is affected by environmental factors.

23
Q

What can affect glycotransferase (GTFs)?

A
  1. presence of glucans ( as can act as an acceptor of unrelated GTF)
  2. proteseases (may modify GTF) and dextranases
24
Q

Why are GTF and FTFs names so damn confusing and wird?

2) What should we use instead?
3) list them for step. mutans

A

name after role however,
A GTF is involved in forming things as well as breakng down sucrose.
There is another naming system to do with solubilities e.g. GTF-S = forms soluble polymer
2) the gene that forms them e.g. in strep mutans there is 3 GTF and 1 FTF. gtfA is not true GTD as makes an ezyme ( sucrose phosphorylase), gtfB makes insoluble mutan , gtfc makes a branched mutan thats partially soluble. gtfD makes a soluble dextran. ftf forms inulin

25
Q

Is pH the same throughout the plaque?

2) Why do strep. mutans form polysaccharides ?
3) How are they able to do this?

A

no very low pH at enamel surface, due to polysaccharides (mostly mutans) formed by microcolonies like strep. mutans

2) strep mutans can bind to the polysaccharides it makes which allows it to properly attach to the biofilm
3) using glucan binding proteins

26
Q

There more than one type fo GBP

True or false

A

true

27
Q

GBP can only be presented as bacterial surface prtoetins

A

false, they are also secreted (some of them)

28
Q

Are GBP homogenous or heterogenous

A

heterogenous

29
Q

How do GBP differ?

A
  1. size
  2. strenght of bond formed with glucan
  3. function ie adhesion/aggregation
30
Q

1) Whats more active in plaque FTF or GTF?
2) Which is present in higher quantities, fructan or glucans?
3) What is the most probable role of fructans in plaque?
4) How is FTF thought to contribute to caries?

A

1) FTF
2) GTF
3) act as a short term energy store
4) by extending the fermentation time of plaque baccteria which will direclty affect acid production (increasing it) OR improve the survival of strep in the plaque

31
Q

What brakes down fructans in plaque?

A

fructanase

32
Q

Other bacteria may adhere to S. mutans via glucan ‘bridges’. Cell-cell adhesion will enhance interspecies interactions. Give 3 interactions between species

A
  • Metabolite cycling
  • Competition
  • Signaling
33
Q

Which of these is the most strongly acidogeneic?

1) bifidobacterium longum
2) Strep. mutans
3) Strep. sanguinis
4) Lactobacillus fermentum
5) Scardovia Wiggssiae

A

4) Lactobacillus fermentum

34
Q

The total amount of plaque present is responsible for dental caries . Is which hypothesis?

A

the non-specific plaque hypothesis

35
Q

Mutans is a group within streptococcus, What is the name of the 2 mutans found in humans?

A

S. mutans

S. sobrinus

36
Q

Veinella utilises ___a___ and produced ___b___ and ___c____

A

a= lactic acid
b=CO2
c=H2

37
Q

What are amyloids?

A

• Amyloids are proteins that form robust fibrils with β-strands running perpendicular to the length of the fibril.

38
Q

What is the role of functional amyloids in plaque?

A
  1. biofilm stabilisation,
  2. melanin formation
  3. the initiation of innate antiviral immune response.
39
Q

What bacterium produces large amounts of extracellular DNA (eDNA)?

2) What targets extracellular DNA to disrupt the biofilms?
3) What effects does it have?

A

1) P. aeruginosa
2) DNase
3) • inhibits plaque formation
• Reduces colonisation by periodontal pathogens

40
Q

Where in the mouth is extracellular DNA present in plaque?

A

subgingival dental plaque (also in plaque on implants)

41
Q

What is plaque fluid?

2) What is its volume equivalent to?
3) Composition: (4)

A 
fluid which fills the spaces between  bacteria in dental plaque 
2) 30% of plaue volume
3) •	saliva (modified) 
•	bacterial metabolites/waste 
•	material leeched from the tooth 
•	gingival fluid
42
Q

1) What is the function of plaque fluid? (3)

which is possible due to the fluids composition

A

1) Acts as a buffer between saliva and tooth.
2) Key role in maintaining Ca2+, PO43-, F-
These ions are reduced in concentration when sucrose is present (not clear why)
3) Can retain antimicrobials or other
components in mouthwash

Stage 2 Microbiology for dentists (25 decks)

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