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Symposia > Oral Microbiology > Flashcards

Oral Microbiology Flashcards

1
Q

How do viruses work?

A

Have nucleic acid surrounded by proteins
Invades a cell and replicates it’s genetic elements inside the cell until it dies

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2
Q

What are bacterial microorganisms?

A

Prokaryotic, unicellular organisms

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3
Q

What are fungi microorganisms?

A

Eukaryotic cells with a rigid cell wall due to chitin
3 types:
1. Yeast (unicellular)
2. Moulds
3. Mushrooms

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4
Q

What are 4 Different types of oral bacteria?

A
  1. Normal flora - expected bacteria to be seen (resident bacteria)
  2. Dental caries - caused by bacteria that weaken the enamel with acid production
  3. Periodontal disease - bacteria feed off soft tissue for energy
  4. Systemic infections - can occur in infants as bacteria cross the placenta
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5
Q

Why is the mouth a good habitat for microbes?

A
  • Mucosa is warm which stimulated bacteria growth
  • Tongue - has rough surface with pits for bacteria to get trapped
  • Saliva - provides a food source for bacteria
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6
Q

How does the oral cavity try to defend against bacteria?

A
  1. Saliva - acts as a buffer, neutralises some of the acid produced by bacteria
  2. Gingival Cervical fluid (GCF) - contains antibodies and found in the gingival crevice
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7
Q

How does bacteria initially enter the oral cavity?

A
  • After birth the oral cavity is quickly invaded by bacteria these are called the Pioneer species
    These are generally gram positive bacteria, these breakdown the Carbohydrates and proteins which produces food for the new bacteria
    Diversity will increase with age generally Sterptococcus is in high concentration
  • Bacteria can also be passed over from the mother via the placenta
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8
Q

How does Gram positive and gram negative bacteria differ?

A
  1. Gram positive has a larger Peptidoglycan layer (crossed linked sugars) than gram Negative bacteria
    This mean when a dye is used Gram positive will be able to hold the dye due to the larger peptidoglycan layer and generally Purple = Gram positive Pink = Gram Negative
  2. Gram positive doesn’t have an outer lipid layer where as gram negative does
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9
Q

How is a bacterial biofilm formed?

A
  1. Acquired Pellicle - a thin layer of salivary glycoproteins deposits on the teeth, these have protein projections (receptors) which start to adhere to bacteria
  2. Adhesion - Bacteria adhere with other bacteria using the receptors and carbohydrate binding proteins called lectins, at this stage acid can break down the adhesion
  3. Co-aggregation - biofilm is formed
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10
Q

What is a Biofilm?

A

A community of microorganism attached to a surface, it’s a multicellular ecosystem

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11
Q

What is plaque?

A

A community of dead and alive bacteria growing in a certain area
Made of
-EPS martix (extra-cellular polymeric substance - polysaccharides)
- DNA from dead and alive bacteria but also the host

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12
Q

What is the conditions deeper in the plaque biofilm?

A
  1. Nutrients - less nutrients deeper in the biofilms often these cell may make up the dead component
  2. O2 - Less o2 available deeper so often these cell are anaerobic
  3. PH - more acidic deeper in the biofilm due to less O2 so no respiration and fermentation happens reassessing lactic acid
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13
Q

What factors effect the oral flora?

A
  1. Saliva
  2. Gingival cervical fluid (GCF)
  3. PH
  4. Redox potential - different bacteria have different needs e.g. anaerobic don’t need O2 whereas capnophilic cells need CO2
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14
Q

What is commensal oral flora?

A

Primary colonisers of the oral cavity
E.g. Coloniser bacteria

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15
Q

How do bacteria grow?

A

Binary fission, average doubling time is 20mins -1hour

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16
Q

Describe a bacteria growth curve?

A
  1. Starts with a low amount of bacteria and this stays the same for a little while, this is the lag phase
    - at this time bacteria are replicating DNA and making new cell walls
  2. Exponential growth - sharpe rise in bacteria numbers
  3. Stationary phase - bacteria numbers plateau at a high level
  4. Death - Bacteria numbers steadily decreases
17
Q

What is the Benefit of biofilm growth for bacteria?

A
  • Can hide form host defences (antibodies can pierce the outer layer)! They also contain the lactamase enzyme that breaks down antibodies
  • Quorum sensing, in a group the bacteria can communicate to lather behaviour/gene expression
18
Q

What is Quorum sensing, and how is it used?

A

What - this is a way of bacteria communicating with each other using protein molecules called autoinducers, these bind to receptors on neighbouring bacteria they change the gene expression to deliver a desired group outcome
- Can be used to communicate with the body

19
Q

Why is plaque bad?

A
  • Bacteria in plaque is effective at:
    1. Getting sugar into the bacterial cells
    2. Catabolising the sugar into acid
    3. Excreting the acid on tooth surfaces
  • can also store sugar when sugar levels are high
  • can initiate unwanted inflammatory responses
20
Q

What does Exogenous source of carbohydrate mean?

A

Carbohydrate source from outside e.g diet sucrose starch lactose

21
Q

What does Endogenous carbohydrates mean?

A

Carbohydrates from inside the body e.g saliva or GCF

22
Q

What process transports sugar transported into cells?

A

Sugar specific transport system which use ATP-dependent membrane permease

23
Q

How does sugar (fructose) enter bacteria? (Using FTF)

A
  1. Sucrose sugar molecules are too large to enter the cells so need to be broken down by FTF - Fructosyl transferase
  2. Sucrose —-> glucose and fructan, glucose can directly enter the cell fructan is still too large and is broken down further by Fructanase
  3. Fructan breaks into fructose and enters cell
24
Q

What is the enzyme FTF?

A

Fructosyl transferase - breaks down sucrose into glucose and fructan

Fructan is also known as insulin

25
Q

What is the enzyme Fructanase?

A

Breaks down fructan into fructose

26
Q

How is second way sugars (sucrose) enter the cells? (Using GTF)

A
  1. Sucrose is broken down by GTF - glucosyl transferase
  2. Sucrose breaks into Fructose and glucans- these aren’t turned over quickly in plaque and act as an energy store
  3. DexA enzyme breaks down glucans into isomaltossaccharides which enter the cell
  4. In the cell the isomaltossacharides are broken down to glucose by DexB
27
Q

What is the difference between DexA and DexB enzymes?

A

DexA - acts outside the cell turning glucans into isomaltossaccharides
DexB - acts in the cell turning isomaltossaccharides into glucose molecules

28
Q

What is the difference between Glucan and fructan?

A

Fructan - rapidly turned over in plaque and used by the cell

Glucan - slow turn over in plaque therefore stored in the plaque as an energy store

29
Q

How does the bacteria catabolise the sugars? (Glucose)

A

2 process
1. Cellular respiration
2. Fermentation
Both begin with glycolysis
- Glucose (C6) —> 2x Pyruvic acid (3C)
Energy realised is stored as ATP

30
Q

How can Glycolysis stage of catabolism be stopped?

A

The enzyme enolase is used to break down the glucose to pyruvic acid, fluoridestops this process

31
Q

How does cellular respiration work?

A
  1. Glycolysis glucose —> Pyruvate (3C)
  2. Using O2 turns into Acetyl Co-A
  3. Krebs cycle and electron transport chain
  4. ATP is produced from ADP
32
Q

What happens in fermentation?

A
  1. Glycolysis - Glucose turns into Puruvate (3C)
  2. With no O2 fermentation happens
  3. Lactic acid and Ethanol are the bi-products
    Acid is excreted out of the cell by membrane pumps and released on tooth surface
33
Q

How is proteins catabolised?

A

Enzyme Peptidase is used

  • high Ph = produced ammonia and acids (deamination)
  • low Ph = produces CO2 and amines (decarboxylation)
34
Q

What happens when plaque is not brushed off?

A

Plaque calcifies and this is called calculus or tartar, these are extracellular deposits with minerals that have hardened around the bacteria

35
Q

What is a cariogenic bacteria?

A

Bacteria that breaks down sugar into acid therefore causes caries by demineralising the enamel with the low Ph acid

36
Q

What is the role of coloniser bacteria?

A

They are generally gram positive bacteria and they breakdown carbohydrates and proteins into smaller molecules for other bacteria to have a food source

Symposia (8 decks)

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