Oral Ecology and Microbial Diversity Flashcards
1
Q
What two methods are used to detect bacterial species?
A
Microscopy and Cultivation
2
Q
Which method of bacterial detection is better for distinguishing between similar morphotypes?
A
Cultivation
3
Q
Detection of bacterial species by cultivation requires specific _______.
A
Nutrients
4
Q
During bacterial cultivation, _______ species and _______ species are overgrown.
A
Minor and Slow-growing
5
Q
True or False: In the oral cavity, 1/4 of all species have been cultivated.
A
False: More than half of the species have been cultivated.
6
Q
What is 16S sequencing?
A
well-established sequencing method used to identify and compare bacteria present within a given sample; good for studying phylogeny and taxonomy
7
Q
Through 16S sequencing, it was determined that there are around _____ species common within the oral cavity.
A
700
8
Q
How many species of bacteria are present in one individual?
A
100-200
9
Q
Because the mouth is an open system, there are _____ and _______.
A
Transient Species and True Residents
10
Q
What is the name of the study that aimed to determine whether individuals share a core microbiome and whether changes in biome correlate to health?
A
Human Microbiome Project
11
Q
True or False: Each person has more bacterial cells than human cells.
A
True
12
Q
Individuals differ among each other, although ______ are shared at distinct body sites.
A
some core species
13
Q
What was the importance of the “Early Contact” study?
A
The study sought to disprove the hygiene hypothesis (don’t kiss your baby to avoid transmission of s.mutans). By studying near-preterm babies that were either home-reared or kept in NICU, the study showed that the array of bacteria present at 3 months was identical.
14
Q
______ is the study of the interrelationships of organisms and their environment.
A
Ecology
15
Q
A ______ is the specific combination of conditions (physical , chemical, or biological) that are necessary for the survival of a particular organism.
A
Niche
16
Q
Thick, stable biofilms on hard surfaces of teeth is also known as _______.
A
Dental plaque
17
Q
Periapical and Odontogenic infections occur after invasion of _______ by micro-organisms.
A
Soft Tissues
18
Q
When discussing different niches in the oral cavity, what are the two broad categories?
A
- Non-shedding (unique) HARD SURFACES
2. Soft Tissue
19
Q
How does the oral ecology change over time?
A
- Acquisition of new organisms from outside the body
2. Changing of oral structures (eruption/loss, pocket formation, injuries)
20
Q
Biofilm thickness _______ over time.
A
Increases
21
Q
What are the soft tissue surfaces to which bacteria adhere?
A
Sulcus, Tongue, Mucosa, Gingiva
22
Q
What are the categories of hard surfaces to which bacteria adhere?
A
- Supra-Gingival Surfaces
2. Subgingival Surfaces
23
Q
What are the most common locations of dental plaque on supra-gingival hard surfaces?
A
- Fissures 2. Proximal Surfaces
24
Q
Bacteria are classified as either _______ or ______.
A
Planktonic or Sessile
25
Which type of bacteria is 1000 times easier to clear than the other?
Planktonic is easier than Biofilms (sessile)
26
_______ bacteria are floating in water.
Planktonic
27
Most bacteria that cause dental problems are _______.
Sessile
28
Which type of bacteria attach to the surface of biofilms?
Sessile
29
Biofilms are made up of _______ and ________ in an aqueous environment.
adherent microorganisms and extracellular matrix
30
What is the glue-like substance that holds the biofilm together and anchors bacteria?
Extracellular Matrix
31
True or False: Water flows through the extracellular matrix via channels.
True
32
Within a biofilm, bacteria are able to detect one another and communicate via ______ ________.
Quorum Sensing
33
What are the three stages of a biofilm life cycle?
1. Attachment
2. Growth
3. Detachment
34
True or False: Biofilms can be formed by a single bacterial species or many species, but cannot include other micro-organisms such as fungi, algae or protozoa.
False: They CAN include other micro-organisms, single, or multiple species.
35
Once bacteria attach to a surface, they ______.
Change (turn on a different set of genes)
36
Why is biofilm bacterial behavior more complex than suspended cell behavior?
Biofilm bacteria live in interactive communities
37
What are the three situations in which biofilm-adaptive genes are turned on?
1. Bacteria detect surfaces
2. Bacteria detect each other
3. Signals pass between bacteria
38
What are four benefits to multiple species co-existing within a biofilm?
1. Provide nutrients for each other
2. Remove toxins
3. Inter/Intra-Species signaling
4. Division of labor within and among species
39
Biofilms are stable, slow-growing communities that are highly resistant to _______, ________, and ________.
Antibiotics
Host Defenses
Mechanical Disruption
40
______ doses that kill suspended cells must be increased by 1000-fold to kill biofilm cells (which would be toxic to the host).
Antibiotic
41
What are the three primary mechanisms for biofilm antimicrobial resistance?
1. Slowing of diffusion
2. Inactive "Persister Cells" repopulate the biofilm
3. Exchange of resistance genes via close proximity
42
Most bacteria in the mouth are NOT _______.
Planktonic (free-floating)
43
True or False: Saliva is a thick film on oral structures.
False. Saliva is just a thin film (a few microns)
44
Biofilms are the cause of many oral problems such as caries, osteomyelitis, _______ and ________.
Periodontitis
| Osteonecrosis
45
Some oral diseases, such as cellulitis, are caused by ______ bacteria, not biofilm bacteria.
invasive
46
What are the six factors that contribute to the oral cavity environment and create specific niches?
1. Bacterial Adherence
2. Oxygen Tension
3. pH
4. Bacterial food supply or substrate
5. Host inhibitory factors
6. Bacterial community interactions
47
Bacteria are able to adhere to host surfaces, other bacteria, and/or ________.
Extracellular Matrix
48
Saliva will promote binding by providing _________ or inhibit binding by _________.
Promotion: Binding Sites
Inhibition: Agglutinating/Clearing
49
Bacteria are able to bind to the host pellicle by binding to components of saliva. What are the four discussed components that bind bacteria?
1. Antibodies
2. Salivary Agglutinins
3. Proline-Rich Glycoproteins
4. alpha-amylase
50
What is the main component of saliva (and oral soft tissues) that will bind bacteria?
Alpha-amylase
51
Oxygen tension is the _______ of oxygen compared to other gases.
partial pressure
52
Compare the percent oxygen (oxygen tension) that is present in a periodontal pocket to the closed mouth and to the air.
Perio pocket = 1-2%
closed mouth = 12-14%
Air = 21%
53
What is the oxygen tension within supragingival plaque? What accounts for the somewhat large range?
1-20%
| the age of the plaque has a large influence on percent
54
_________ is the electrical potential or tendency to oxidize/reduce (oxygen level)
Oxidation-Reduction Potential (Eh)
55
A positive Eh aerobe will have ______ oxygen. A negative Eh anaerobe will have _______ oxygen.
+ high
| - low
56
_______ require oxygen at atmospheric levels in order to grow.
Obligate Aerobes
57
______ can switch between aerobic and anaerobic metabolism.
Facultative Anaerobes (or faculatative aerobes)
58
Which kind of microorganism requires low levels of oxygen?
microaerophilic
59
Which type of microorganism thrives without oxygen but will tolerate its presence?
Aerotolerant anaerobe
60
______ do not use oxygen as a nutrient and are killed or inhibits by it.
Obligate anaerobes
61
Which type of microorganism will not be found in the oral environment? What is the oxygen tension in a closed mouth?
Obligate anaerobes
| 12-14% oxygen
62
_________ causes oxidation of membrane lipids which leads to destruction of cell integrity, and oxidation of enzyme sulfhydryl groups resulting in cross-linking (inactivity).
Oxygen Toxicity
63
The genetic inability to make ________ is the cause of anaerobic sensitivity to oxygen.
Enzymes:
SOD (superoxide dismutase)
catalase
peroxidases
64
What happens when aerobes face oxygen without the appropriate enzymes present?
oxygen products (superoxide and peroxide) cause damage to cellular constituents
65
What three important enzymes are responsible for detoxifying oxygen radicals that are generated by living systems in the presence of oxygen?
Superoxide Dismutase
Catalase
Peroxidase
66
Why does older plaque have a lower Eh?
Eh (oxidation-reduction potential)
| older plaque gets thick and becomes sheltered from oxygen. This causes a change in the microflora
67
What species are typically found in the sulcus or mature coronal plaque?
Anaerobic (these sites are protected from oxygen)
68
What species are found in supragingival plaques?
facultative and microaerophilic
69
_________ species scavenge oxygen and help to provide an anaerobic environment for other species.
Fusobacterium
70
Ingested foods indirectly affect pH through bacterial fermentation of sugar to _______.
Lactate
| pH= 5
71
The inflammation within periodontal pockets creates an environment with a pH around _____.
7.5
72
____ pH inhibits most oral species except strep and lactobacilli.
low
| strep and lactobacilli are "acid tolerant"
73
Supragingival pH is _______ than subgingival pH.
lower
74
Supragingival oxygen is _______ than subgingival.
higher
75
What are the two major physical nutrient niches in the oral cavity?
1. Subgingival
| 2. Supragingival
76
The supragingival environment includes endogenous _______ and exogenous _______.
saliva
| ingested foods
77
The subgingival environment includes _______ fluid and cells.
crevicular
78
True or False: The subgingival environment contains exogenous components.
False: only endogenous, ingested nutrients do NOT reach subgingivally
79
Based on bioavailability, the nutrients sources in the oral cavity are either _______ or _________.
1. Low molecular weight, soluble carbs and amino acids
| 2. Starches and proteins
80
What type of ingested nutrient is readily taken up by bacteria?
low molecular weight, soluble carbs or amino acids
81
What type of ingested nutrient must be retained in order for bacterial digestion to occur?
starches and proteins
82
Saliva contains glycoproteins, inorganic salts, amino acids, glucose, and vitamins which is only available to ______ inhabitants.
SUPRAgingival
83
What are the four discussed endogenous nutrient sources?
1. saliva
2. shed host cells
3. gingival crevicular fluid
4. breakdown products of periodontal tissue
84
_________ contains tissue and serum proteins, amino acids, glucose, vitamins, hemin, and hormones.
Gingival crevicular fluid
85
The _____ and ______ of gingival crevicular fluid is influenced by degree of inflammation.
flow and composition
86
Tube-fed patients have an abundance of both supra and subgingival plaque because ______ nutrients are sufficient.
endogenous
87
Why are endogenous nutrients not sufficient for caries formation?
Because exogenous carbohydrates are required
88
Host inhibitory factors include ______immunity, ______immunity, and ______.
Innate
Specific
Saliva
89
What are three important mechanisms of host antibodies?
1. Inhibit colonization
2. act as opsonins
3. activate complement system
90
Which immunoglobulin in saliva is important for preventing adhesion?
salivary Ig A
91
Which immunoglobulin acts in crevicular fluid to directly combat periodontal organisms?
Ig G
92
________ are a component of innate immunity and account for 95% of leukocytes in crevicular fluid.
neutrophils
93
True or False: Neutrophils are abundantly present throughout the mouth.
False: neutrophils are not active supragingivally
94
Antimicrobial peptides are produced in the _______ and participate in innate immunity.
salivary glands
95
What are the two MAJOR salivary proteins?
alpha-amylase
| mucins
96
Which salivary protein is important for digestion of starch and binding of bacteria?
alpha amylase
97
Which salivary protein acts as a lubricant?
mucin
98
What are the seven minor salivary proteins?
1. Lysozyme
2. lactoferrin
3. serum transferrin
4. sialoperoxidase
5. antimicrobial peptides
6. acidic proline-rich
7. statherin
"Some Silly Ladies Act Stupid And Lazy"
99
Salivary ______ digests peptidoglycan in the bacterial cell wall, leading to osmotic disruption and cell death.
lysozyme
100
Which two minor salivary proteins are responsible for binding iron so that it is not available to bacteria?
lactoferrin and serum transferrin
101
_______ generates superoxide radicals which inactivate bacterial enzymes and lead to bacterial death.
sialoperoxidase
102
Which salivary component acts against bacteria and yeast to create porins?
antimicrobial peptides
103
Which two salivary components protect the mineral integrity of oral structures by modulating calcium and phosphate chemistry?
acidic proline-rich proteins and statherin
"To maintain Calcium and Phosphate you must....follow the STAT- IC PRO"
104
What are the two mechanisms for maintaining the integrity of teeth?
1. pellicle proteins/salivary minerals
| 2. salivary buffering
105
What are the two discussed bacterial products that are used by other bacteria as nutrients?
```
Lactic Acid (metabolized sugar)
Vitamin K3 (menadione)
```
106
Veillonella is a critical component of the bacterial food chain. Veillonella soaks up lactate byproducts and converts it to ________ which in turn raises the pH for acid-sensitive strep.
propionate
107
Which bacterial product is used by P. gingivalis (perio disease) after it is synthesized by Veillonella?
menadione (vitamin K3)
108
_____ and _____ are bacterial products whose presence or absence will alter the environment and allow specific bacteria to thrive.
Carbon dioxide
| oxygen
109
_______ are bacterial inhibitory factors that are produced by one bacteria and inhibit another.
bacteriocins
110
What is colonization resistance?
established organisms occupy a certain niche and prevent establishment of new strains
111
Is pH greater for subgingival or supragingival environments?
subgingival
112
Which niche is able to utilize ingested nutrients?
supragingival bacteria
113
What are the two major oral niches (ecosystems)?
1. Supragingival tooth surface and dorsum of tongue
| 2. gingival crevice (subgingival tooth and crevicular epithelial surfaces
