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Oral Microbiology > Oral Ecology and Microbial Diversity > Flashcards

Oral Ecology and Microbial Diversity Flashcards

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Biology 101 flashcards
1
Q

What are the two traditional methods used to detect bacterial species?

A
  1. microscopy

2. cultivation

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2
Q

What is difficult to distinguish when doing microscopy?

A

difficult to distinguish similar morphotypes

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3
Q

With cultivation, there are special ___ required, ___ of some species by others, minor species and slow growing species ___.

A

nutrients; inhibition; overgrown

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4
Q

List three newer methods to detect bacterial species.

A
  1. 16 S sequencing
  2. rDNA gene alignments
  3. construct phylogenetic trees
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5
Q

How many organisms are detected in the oral cavity if using cultivation methods? 16 S sequencing?

A

cultivation - 300+ species

16 S sequence - 700 species

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6
Q

Each person harbors ___-___ species.

A

100-200

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7
Q

The mouth is an ___ system. We have ___ species vs ___ residents of the oral cavity that grow.

A

open; transient; true

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8
Q

T/F. Contact with water, soil, plants, animals, other humans, other body sites leads to surprising bacterial diversity, both in species that are adapted to the oral cavity and grow there, and transient species that may be detected on occasion.

A

True.

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9
Q

What project worked to determine whether individuals share a core human microbiome and whether changes in the human microbiome can be correlated with changes in human health?

A

Human Microbiome Project

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10
Q

T/F. The Human Microbiome Project developed new technological and bioinformatic tools needed to support its goals, but it did not address ethical, legal and social implications raised by its research.

A

False, the project developed new technological and bioinformatic tools needed to support its goals, AND addressed ethical, legal and social implications raised by its research.

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11
Q

T/F. Each of us includes more human cells than bacterial cells.

A

False, we include more BACTERIAL cells THAN human cells.

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12
Q

T/F. Our microbiota includes many-fold more DNA variety than our human genome.

A

True

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13
Q

T/F. Each body site harbors a distinct microbial community, including the oral cavity.

A

True.

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14
Q

T/F. Most individuals are similar to each other and they share the same core species.

A

False, Individuals DIFFER amongst each other, although some core species are shared.

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15
Q

Diversity of the human microbiome is unique to each ___, and strongly determined by ___ habitat.

A

individual; microbial

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16
Q

Describe the hygiene hypothesis.

A

babies are kept too clean and this alters their immune system

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17
Q

In the acquisition of the human oral microbiome, how much does human contact affect babies from getting oral bacteria?

A

NICU vs home babies had different bac 1 day after delivery however by 2wks and at 3 months NICU babies which had minimum touch compared to Home babies had the same bacterial oral microbiome as Home babies.

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18
Q

___ is the study of the interrelationships of organisms and their environment.

A

Ecology

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19
Q

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

A

niche

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20
Q

In multiple niches, different oral sites can harbor different bacteria? Describe how non-shedding hard surfaces of teeth are different from micro-organisms that invade soft tissues.

A

Non-shedding hard surfaces of teeth - microorganisms can form stable, thick biofilms called “dental plaque”
Micro-organisms can invade soft tissues - as in periapical and odontogenic infections.

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21
Q

The oral ecology changes over time by the acquisition of organisms. How do oral structural changes affect the oral ecology?

A

teeth erupt and are lost
pockets form (cause by bacteria)
injuries occur

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22
Q

Biofilm thickness increases over time. How does succession occur?

A

when surfaces are cleaned

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23
Q

What are the soft tissue surfaces to which bacteria adhere?

A

sulcus, tongue, mucosa, gingiva

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24
Q

On hard oral surfaces, there are visible biofims called ___ ___.

A

dental plaque

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25
Q

What are some SUPRA-gingiva hard surfaces to which bacteria adhere?

A

fissures (most common), proximal surfaces, buccal and lingual enamel, cementum, restorations, calculus, dorsum of tongue

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26
Q

What are some SUB-gingival hard surfaces to which bacteria adhere?

A

enamel, cementum, restorations, calculus

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27
Q

Some bacteria are ___ - floating in water (unattached). Most bacteria that cause dental problems and many medical problems are ___ - attached to a surface in biofilms.

A

planktonic; sessile

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28
Q

What are biofilms made up of?

A

adherent microorganisms and extracellular matrix in an aqueous environment

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29
Q

Bacteria adhere to surfaces in an ___ environment and excrete a slimy, glue-like substance that can ___ them to surfaces. The sticky material that holds the biofilm together is called ___ ___. ___ flows thru channels in the matrix.

A

aqueous; anchor; extracellular matrix; water

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30
Q

What are the steps of the biofilm life cycle?

A
  1. attachment
  2. growth of mature biofilm community
  3. detachment of cells to seed new biofilm formation
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31
Q

T/F. Biofilms can be formed by a single bacteria species.

A

True, more often biofilms include many species of bacteria.

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32
Q

T/F. Biofilms can include other organisms such as fungi, algae and protozoa. This is known as a polymicrobial community.

A

True.

33
Q

Once bacteria attach to a surface, they change by turning on a different set of ___.

A

genes.

34
Q

When are bio-adaptive genes turned on?

A
  1. Bacteria detect surfaces
  2. bacteria deter each other (quorum sensing)
  3. signals pass between bacteria
35
Q

Why do multiple species co-exist and even cooperate?

A
  1. provide nutrients for each other (food chains)
  2. remove toxins
  3. inter- and intra-species signaling is important
  4. “division of labor” within the same species and among species
36
Q

Biofilms are stable, slow-growing communities that are highly resistant to ___, host defense and ___ disruption.

A

antibiotics; mechanical

37
Q

T/F. Control strategies that work on suspended cells also work on biofilm cells.

A

False, control stategies that work on suspended cells are LESS EFFECTIVE on biofilm cells.

38
Q

Antibiotic doses that kill suspended cells need to be increased as much as ___-fold to kill biofilm cells.

A

1000

and these amounts would be impractical or toxic to the host

39
Q

___ rates for biofilm cells are far below planktonic kills by antimicrobials.

A

Disinfection

40
Q

The primary mechanism for biofilm antimicrobial resistance is slowing of ___, “___ cells” that are alive but metabolically inactive survive and repopulate biofilm, and close proximity and exchange of ___ genes.

A

diffusion’ persister; resistance

41
Q

Most bacteria in the mouth are not free floating as in a liquid culture. Why?

A

because saliva is a thin film a few microns thick on oral structures

42
Q

In addition to caries and periodontitis, what other oral problems are biofilms the cause?

A

osteomyelitis and osteonecrosis secondary to bisphosphonate therapy (anti-osteoclastic drug)

43
Q

What is the cause of oral diseases like cellulitis?

A

caused by invasion of bacteria, not biofilm bacteria. BUT the infection originated with biofilm on tooth

44
Q

What are surface sites for bacterial adherence?

A
  1. host surfaces (receptor molecules)
  2. direct bacterial interactions
  3. extracellular matrix
45
Q

Salivary binding promotes bacterial adherence by providing ___ sites or inhibits ___ and ___. What are some of these salivary factors?

A

binding; aggultinating; clearing

antibodies (acquired immunity)
salivary agglutinins
proline-rich glycoproteins
alpha-amylase

46
Q 
What is the oxygen tension of the following:
air
closed mouth
periodontal pocket
supragingival plaque
A

air - 21%
closed mouth - 12-14%
periodontal pocket - 1-2%
supragingival plaque - 1-20% depending on age of plaque

47
Q

The ___-___ potential is an electrical potential or tendency to oxidize or reduce oxygen levels. It is used to measure oxygen.

A

oxidation-reduction

48
Q

A postive Eh = ___ species with ___ oxygen. A negative Eh = ___ species with ___ oxygen.

A

aerobe; high; anaerobes; low

49
Q

___ aerobes require O2 at atmospheric levels for growth. ___ anaerobes (or ___ aerobes) can switch between aerobic and anaerobic metabolism. ___ require low levels of O2.

A

Obligate; Facultative; facultative; microaeophilic

50
Q

___ anaerobes have anaerobic metabolism but tolerate the presence of O2. ___ anaerobes (occassionally called ___) do not use O2 as a nutrient, and O2 is toxic - kills or inhibits growth.

A

Aeortolerant; Obligate; aerophobes

51
Q

Oxygen toxicity cause oxidation of membrane ___ and destruction of cell ___. It also causes oxidation of ___ groups in enzymes resulting in ___-___ and inactivity.

A

lipids; integrity; sulfhydryl; cross-linking

52
Q

What is the sensitivity of anaerobes to oxygen due to?

A

the genetic inabiligy to make enzymes such as superoxide dismutase, catalase, and peroxidases

53
Q

What is the action of superoxide dismutase, catalase, and peroxidases?

A

these enzymes detoxify oxygen radicals that are generated by living systems in the presence of O2

54
Q

Older plaque gets thick and becomes sheltered from oxygen. What is its Eh?

A

Eh is low and corresponding shift in microflora (succession)

55
Q

Where are anaerobic, facultative and microaerophilic species found?

A

anaerobic - O2-protected sites such as the sulcus or mature coronal plaque
facultatitive and microaerophilic - in supragingival plaques

56
Q

What is example of a species that scavanges O2 to help provide an anaerobic environment for other species?

A

fusobacterium

57
Q

How does ingested food affect the pH?

A

directly (carbonated soft drink pH = 3)

indirectly (bacterial fermentation of sugars to lactate pH =5)

58
Q

pH normally ranges from ___ to ___ in periodontal pocket

A

5.0 (resulting from sugar fermentation to lactic acid); 7.5 (resulting from inflammation)

59
Q

Low pH inhibits most oral species except?

A

Acid tolerant (aciduric) strep and lactobacilli

60
Q

SUB gingiva has a ___ pH and ___ O2

SUPRA-gingiva has a ___pH and ___ O2

A

SUB - high pH, low O2

SUPRA - low pH, high O2

61
Q

What are the two major physical NUTRIENT NICHES in the oral cavity?

A

SUPRAgingival - saliva, ingested food

SUBgingival - crevicular fluid and cells

62
Q

Exogenous (ingested) nutrients are important for ___-gingival residents and not ___-gingival residents because they do not reach the sulcus.

A

Supra-; sub-

63
Q

T/F. High molecular weight, insoluble carbohydrates and amino acids are readily taken up by bacteria. Starches and proteins are not digested well by bacteria. The frequency of ingestion is not important.

A

False, LOW molecular weight, SOLUBLE carbohydrates and amino acids are readily taken up by bacteria. Starches and proteins ARE retained (sticky foods) for bacterial digestion to occur. The frequency of ingestion IS important

64
Q

Saliva is an ___ nutrient source that is only available to ___-gingival inhabitants and contains glycoproteins, inorganic salts, amino acids and glucose, and vitamins.

A

endogenous; supra

65
Q

What sheds host cells by lysis?

A

hypotonic saliva

66
Q

Gingival ___ fluid is a serum transudate whose flow and composition is influenced by the degree of ___. It contains tissue and serum proteins, amino acids, glucose, vitamins, ___ (especially in gingivitis), and hormones (estradiol and progesterone).

A

crevicular; inflammation; hemin

67
Q

T/F. Breakdown products from periodontal tissues from bacterial proteases and host causes inflammatory degradation of host tissues.

A

True.

68
Q

T/F. Endogenous tissues are sufficient to form plaque and caries.

A

False, it IS sufficient to form plaque (tube-fed) BUT NOT caries - exogenous carbohydrates needed.

69
Q

What antibody is found in saliva that prevents adhesion? Which antibody is found in crevicular fluid and is directed against periodontally important organisms?

A

sIgA

IgG

70
Q

List some examples of innate immunity.

A
  1. epithelial barrier and desquamation (soft tissue)
  2. saliva flow
  3. neutrophils (95% in crevicular fluid) - not found in saliva or supragingivially. lost of neutrophils = early onset of perio disease
  4. complement proteins from crevicular fluid
  5. antimicrobial peptides produced in salivary glands, epithelium and immune cells defensins, histatins, and cathelicidins
71
Q

What are the two major salivary proteins and what are their functions?

A

alpha-amylase - digest starches and binds bacteria

mucins - lubricants

72
Q

What is the role of these minor salivary proteins?

  1. salivary lysozyme
  2. salivary lactoferrin and serum transferrin
  3. sialoperoxidase system
  4. antimicrobial peptides
  5. acidic proline-rich proteins and staherin
A
  1. digests peptidoglycan in bacterial cell wall leading to osmotic disruption and cell death
  2. proteins that bind iron so that it is not bioavailable to bacteria
  3. generates superoxide radicals which inactivate bacterial enzymes leading to bacterial death
  4. activity against bacteria and yeast
  5. modulate salivary calcium and phosphate chemistry
73
Q

What are some mechanisms for maintaining integrity of tooth?

A

pellicle proteins/salivary minerals

salivary buffering

74
Q

What is produced by metabolism of sugars by Streps and required by Veillonella?

A

lactic acid

75
Q

Veillonella convert lactate to ___ to ___ pH for acid-sensitive strep

A

propionate; raise

76
Q

What is synthesized by Veillonella parvula and used by P. gingivalis and P. intermedia?

A

vitamin K3 (menadione)

77
Q

Give two examples of how bacteria products alter the environment.

A

Carbon dioxide produced by a number of organisms including peptostreptococci and Eubacteria enhance the growth of Capnocytophaga and A. actinomycetemcomitans

Removal of oxygen by Fusobacterioum nucleatum/periodonticum so that more fastidious anaerobes such as Tanerella forsythia can survive.

78
Q

What is a bacteriocin?

A

bacterial inhibitory factor

Streptococcus salivarius produces enocin that inhibits S. pyogenes (strep throat)

79
Q

Describe colonization resistance.

A

Established organisms occupy niche preventing establishment of new strains.

Oral Microbiology (11 decks)

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