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Oral Microbio > Oral Ecology and Microbial Diversity > Flashcards

Oral Ecology and Microbial Diversity Flashcards

1
Q

What are the “Traditional Methods” of detecting bacterial species?

A

Microscopy

Cultivation

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2
Q

What is a problem with Microscopy?

A

Difficult to distinguish between similar morphotypes

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3
Q

What are some problems with microbial Cultivation?

A

There are special nutrient requirements
Inhibition of some species by others
Minor species can get overgrown
Slow growing species can get overgrown

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4
Q

What is the 16S Sequencing?

A

The new method to detecting bacterial species

-rDNA gene alignments and construct phylogenetic trees

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5
Q

T/F - All oral bacteria have been cultivated

A

False - only about half the species found in the oral cavity have been cultivated

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6
Q

How many organisms are present in the oral cavity?

A

Lots

  • 300+ by cultivation
  • 700 by 16S sequence diversity
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7
Q

How many species of oral microbes does an individual harbor?

A

100-200

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8
Q

What is the effect of the mouth being an open system?

A

Contact with water, soil, plants, animals, other humans, other body sites leads to transient species and true resident species

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9
Q

What were the goals of the Human Microbiome Project?

A

Determine whether individuals share a core humane microbiome
Understand whether changes in the human microbiome can be correlated with changes in health
Develop new technologies to support these goals
Addressing the ethical, legal, and social implications raised by microbiome research

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10
Q

Do we have more human cells or bacterial cells in our system?

A

Bacterial cells

And that microbiota contains many-fold more DNA variety than our humane genome

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11
Q

T/F - Microbial communities are the same throughout the body

A

False - Each body site harbors a distinct microbial community, including the oral cavity

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12
Q

T/F - Everyone has the same microbiota

A

False - Individuals differ amongst each other, although some core species are shared

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13
Q

What does Bray-Curtis show us?

A

A graph that shows diversity among subjects by body habitat

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14
Q

Where do humans acquire their human oral microbiome?

A

Parents kissing them

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15
Q

What is the hygeine hypothesis? Why is it wrong?

A

It says “don’t kiss babies or share utensils to avoid transmission of S. mutans”
It’s wrong because otherwise babies don’t develop normal microbiota as well

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16
Q

How do home-reared babies v babies in the NICU develop oral microbiota?

A

They both develop the same microbiota, but babies that were in the NICU take a little bit longer to develop it

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17
Q

Ecology

A

The study of interrelationships of organisms and their environment

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18
Q

Niche

A

The specific combination of conditions that are necessary for the survival of a particular organism
These parameters may be physical, chemical, and biological

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19
Q

Mutliple niches can be found in the oral cavity. Where would different niches be found?

A

In different oral sites - they can harbor different bacterial species

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20
Q

What are the two most noticeable niches in the oral cavity?

A

Non-shedding, hard tooth surface - where biofilm/plaque can accumulate
Soft tissues - micro-organisms can invade and cause periapical and odontogenic infections

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21
Q

How can oral ecology change over time?

A

Oral structure change:

  • Teeth erupt and are lost
  • Pockets can form
  • Injuries occur
  • biofilm thickness changes
  • If surfaces are cleaned, succession occurs
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22
Q

What are some examples of soft-tissue surfaces?

A

Sulcus
Tongue
Mucosa
Gingiva

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23
Q

What are the supra-gingival hard surfaces where biofilm can accumulate?

A 
Fissures
Proximal surfaces
Buccal and lingual enamel surfaces
Cementum
Restorations
Calculus
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24
Q

What are the sub-gingival hard surfaces where biofilm can accumulate?

A

Enamel
Cementum
Restorations
Calculus

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25
Q

Planktonic bacteria

A

Bacteria floating in water

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26
Q

Most of the bacteria that cause dental/medical issues are in what form?

A

Sessile - Attached to surfaces in a biofilm

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27
Q

What are biofilms made up of?

A

Adherent microorganisms and ECM in an aqueous environment

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28
Q

What is the purpose of the ECM in a biofilm?

A

It is the sticky material that holds the biofilm together
The reason biofilms are hard to get rid of
Contains water flow through channels that act like a circulatory system

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29
Q

What is the biofilm lifecycle?

A

Attachment
Growth to mature biofilm community
Detachment of cells to seed new biofilm formaiton

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30
Q

Polymicrobial communities

A

Can be formed by a single bacterial species
Biofilms are an example
May also include other micro-organisms such as fungi, algae, protozoa

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31
Q

Why are biofilms more complex than planktonic bacteria?

A

They turn on a different set of genes
Multiple species cooperate
Highly resistant to antibiotics

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32
Q

When are biofilm adaptive genes turned on?

A

When bacteria detect surfaces
When bacteria detect each other (quorum sensing)
Signals pass between bacteria

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33
Q

What can bacteria in a biofilm do to co-exist and cooperate?

A

Provide nutrients to each other (food chains)
Remove toxins
Inter- and intra- species signaling
“Division of labor”

34
Q

What are biofilms highly resistant towards?

A

Antibiotics
Host defenses
Mechanical disruption

35
Q

T/F - You need more antibiotics to kill biofilms than planktonic bacteria?

A

True - up to 1000-fold, which ends up being toxic to the host

36
Q

What are the factors that contribute to the environment in the oral cavity and create specific niches?

A 
Bacterial adherence
Oxygen tension
pH
Bacterial food supply or substrate
Bacterial community interactions
37
Q

What effect does saliva have on bacterial adherence?

A

Promotes by providing binding sites

Inhibit by agglutinating and clearing

38
Q

How much oxygen is in an open mouth?

A

21%

39
Q

How much oxygen is in a closed mouth?

A

12-14%

40
Q

How much oxygen is in the periodontal pocket?

A

1-2%

41
Q

How much oxygen is in supragingival plaque?

A

1-20% depending on the age of the plaque
(newer, thin plaque has more)
(older, thicker plaque has less)

42
Q

What is Oxidation-reduction potential?

A

Electrical potential or tendency to oxidize or reduce (aka the oxygen level)
Positive Eh aerobes = high oxygen
Negative Eh anaerobes = low oxygen

43
Q

Obligate aerobes

A

Require O2 at atmospheric levels for growth

44
Q

Facultative anaerobes

A

Can switch between aerobic and anaerobic metabolism

45
Q

Microaerophilic

A

Require low levels of O2

46
Q

Aerotolerant anaerobes

A

Anaerobic metabolism, but tolerate the presence of O2

47
Q

What can oxygen toxicity cause?

A

Oxidation of membrane lipids and destruction of cell integrity
Oxidaiton of sulfhydryl groups in enzymes resulting in cross-linking and inactivity (damage proteins)
This is done by oxygen free radicals

48
Q

What makes anaerobes sensitive to oxygen?

A

Genetic inability to make enzymes such as superoxide dismutase (SOD), catalase, or various peroxidases

49
Q

What is the action of superoxide dismutase?

A

Take superoxides and converted them to O2 and peroxide

50
Q

What is the action of peroxidases?

A

Take oxygen and peroxide and convert them to 2 H20 molecules

51
Q

What is the action of catalase?

A

Take oxygen and two peroxide and make water and oxygen

52
Q

What happens to older plaque?

A

It gets thicker and becomes sheltered from oxygen. This lowers Eh and has a corresponding shift in microflora (succession)

53
Q

Where is the mouth are anaerobic species found?

A

In oxygen-protected sites such as the sulcus and mature plaque

54
Q

Where in the mouth are facultative anaerobes and microaerophilic species found?

A

Supragingival plaques

55
Q

What is the significance of Fusobacterium species?

A

Scavenge oxygen and help provide an anaerobic environment for other species

56
Q

What is normal oral pH?

A

7.0-7.2

57
Q

How can ingested foods directly affect pH?

A

Carbonated drinks have a pH of 3 and can drop it

58
Q

How can ingested foods indirectly affect pH?

A

Bacterial fermenting of sugars to lactic acid has a pH of about 5

59
Q

What can periodontal pocket pH of 7.5 be a result of?

A

Inflammaiton

60
Q

What are the critical ecological determinants of caries?

A

Bacteria
Substrate
Vulnerable tooth

61
Q

What are the two MAJOR nutrient niches in the oral cavity?

A

Supragingival

Subgingival

62
Q

Where do supragingival environment nutrients come from?

A 
Saliva (endogenous)
Ingested food (exogenous)
63
Q

Where do nutrients in the subgingival environment come from?

A

Crevicular fluid and cells (endogenous)

64
Q

What does it mean for ingested nutrients to be ‘bioavaliable’?

A

Low molecular weight

Soluble carbohydrates and amino acids are readily taken up

65
Q

What is in saliva that can be used for nutrients?

A 
Glycoproteins
Inorganic salts
Amino acids
Glucose
Vitamins
66
Q

What are examples of endogenous nutrient sources

A

Saliva
Shed host cells
Gingival crevicular fluid
Breakdown products of perio tissues

67
Q

What is in crevicular fluid that can be used for nutrients?

A 
Serum proteins
Amino acids
Glucose
Vitamins
Hemin
Hormones
68
Q

sIgA

A

Secretory immunoglobulin A
In the saliva
Prevents adhesion

69
Q

IgG

A

In gingival crevicular fluid

Directed against periodontally important organisms

70
Q

What role do antibodies play in the oral cavity?

A

Inhibit colonizaiton
Act as opsonins (mark bacteria for targeting)
Activate compliment system

71
Q

What makes up the innate immunity in the oral cavity?

A 
Epithelial barrier
Desquamation of soft tissues
Neutrophils
Complement proteins in crevicular fluid
Antimicrobial peptides
72
Q

What are the major salivary proteins?

A

a-amylase

mucins

73
Q

a-amylase

A

Digests starches and binds bacteria

74
Q

Mucins

A

lubricant in saliva

75
Q

What are salivary defenses (minor proteins)

A 
Salivary lysozyme
Salivary lactoferrin 
Serum transferrin
Sialoperoxidase system
Antimicrobial peptides
Acidic proline-rich proteins
76
Q

Salivary lysozyme

A

Digests peptidoglycans in bacterial cell wall leading to osmotic disruption and cell death

77
Q

Salivary lactoferrin and serum transferrin

A

Proteins that bind iron so that it is not bioavailable to bacteria

78
Q

Sialoperoxidase sustem

A

Generates superoxide radicals which inactivate bacterial enzymes leading to bacterial death

79
Q

What mechanisms are used to maintain the integrity of the tooth?

A

Pellicle proteins/salivary minerals

Salivary buffering

80
Q

What do pellicle proteins do?

A

Keeps the tooth from getting dissolved

81
Q

What bacterial products can be used as nutrients for microbes?

A

Lactic acid

Vitamin K3

82
Q

What bacterial products can alter the environment?

A

Carbon dioxide

Removal of oxygen by Fusobacterium

Oral Microbio (11 decks)

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