Lecture 1 - Ecology & Microbial Diversity

Question 1

What are the traditional methods by which we detect bacterial species?

Answer 1

• Microscopy
• Cultivation
• DNA methods

Question 2

In the oral cavity, more than ____ of species have been cultivated.

Answer 2

half

Question 3

Each person harbors around ___ species? (how many)

Answer 3

200

Question 4

Within our bodies, we have slightly ____ bacterial cells than human cells. (more or less)?

Answer 4

more

Question 5

Our microbiota includes much more ___ variety than our human genome.

Answer 5

DNA

Question 6

The study of the interrelationships of organisms and their environment.

Answer 6

Ecology

Question 7

The specific combination of conditions that are necessary for the survival of a particular organism. Parameters may be physical, chemical, or biological.

Answer 7

Niche

Question 8

T/F

There are multiple niches within the oral cavity because different oral sites harvest different bacterial species.

Answer 8

True

Question 9

Examples of soft tissue surfaces in the oral cavity to which bacteria adhere are:

Answer 9

• sulcus
• tongue
• mucosa
• gingiva

Question 10

Hard surfaces develop a visible biofilm called:

Answer 10

dental plaque

Question 11

Some bacteria are ________, meaning they are free-floating in water.

Answer 11

planktonic

Question 12

Most of the bacteria that cause dental problems and many medical problems are _______ and are attached to a surface in biofilms.

Answer 12

sessile

Question 13

Biofilms are made up of what 2 things within an aqueous environment?

Answer 13

• adherent microorganisms

- extracellular matrix

Question 14

Bacteria excrete a slimy, glue-like substance that helps adhere them to surfaces. It also hold the biofilm together. What is the substance?

Answer 14

Extracellular matrix

Question 15

Describe the biofilm lifecycle.

Answer 15

• attachment
• growth to mature biofilm community
• detachment of cells to seed new biofilm formation

Question 16

T/F

Biofilm can be formed by a single bacterial species.

Answer 16

True

Question 17

T/F
More often, biofilms include many species of bacteria, but do not include other microorganisms such as fungi, algae, or protozoa.

Answer 17

False

Biofilms may also include fungi, algae, or protozoa.

Question 18

T/F
Biofilms are stable, slow-growing communities that are highly resistant to antibiotics, host defenses, and mechanical disruption.

Answer 18

True

Question 19

Antibiotic doses that kill planktonic cells need to be increased as much as ____-fold to kill biofilm cells (impractical/toxic)

Answer 19

1,000

Question 20

Primary mechanisms for biofilm antimicrobial resistance include:

Answer 20

• slowing of diffusion
• “persister cells” (alive, but metabolically inactive)
• close proximity and exchange of resistance genes

Question 21

What are the 6 ecological determinants that contribute to the environment in the oral cavity and create specific niches?

Answer 21

• Bacterial adherence
• Oxygen tension (Eh)
• pH
• Bacterial food supply or substrate (nutrients)
• Host inhibitory factors
• Bacterial community interactions

Question 22

Host surfaces, direct bacterial interactions, and extracellular matrix provide surface sites for _________.

Answer 22

adherence

Question 23

This can either promote (provides binding sites) or inhibit (agglutinating and clearing) in regard to bacterial adherence.

Answer 23

Salivary binding

Question 24

The percentage of oxygen in the air is about __%, whereas in the closed mouth it’s about __-__%.

Answer 24

21%

12-14%

Question 25

This is the electrical potential or the tendency to oxidize or reduce (oxygen level).

Answer 25

Oxidation-Reduction Potential (Eh)

Question 26

This type of microorganism requires O2 at atmospheric levels for growth.

Answer 26

obligate aerobe

Question 27

This type of microorganism can switch between aerobic and anaerobic metabolism

Answer 27

facultative bacteria

Question 28

This type of microorganism does not use O2; in fact, O2 is toxic and can kill the microorganism or inhibit growth.

Answer 28

anaerobe

Question 29

Oxygen toxicity causes oxidation of what two things?

Answer 29

- membrane lipids (destruction of cell integrity) | - sulfhydryl groups in enzymes (cross-linking and inactivity)

Question 30

The sensitivity of anaerobes is due to the genetic inability to make enzymes such as (which 3 enzymes)?

Answer 30

- superoxide dismutase - catalase - peroxidases

Question 31

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

Answer 31

They detoxify oxygen radicals that are generated by living systems in the presence of O2.

Question 32

What types of species might you find in supragingival plaques?

Answer 32

- facultative | - microaerophilic

Question 33

This species scavenges O2 and helps to provide an anaerobic environment for other species.

Answer 33

Fusobacterium

Question 34

Normal oral pH is ...?

Answer 34

7.0

Question 35

Low pH inhibits most oral species except acid tolerant species such as...?

Answer 35

- Strep | - Lactobacilli

Question 36

According to Griffen's lecture, what three factors are needed for development of caries?

Answer 36

- bacteria - substrate - vulnerable tooth

Question 37

What are the two major physical nutrient niches in the oral cavity?

Answer 37

- supragingival environment (saliva and ingested food) | - subgingival environment (crevicular fluid and cells)

Question 38

Ingested food is an example of an _________ nutrient source for microbes.

Answer 38

exogenous

Question 39

Endogenous nutrient sources for microbes include:

Answer 39

- saliva - shed host cells - gingival crevicular fluid - breakdown products from periodontal tissues

Question 40

T/F | Endogenous nutrients are sufficient for plaque, but exogenous nutrients (i.e. carbs) are needed for caries.

Answer 40

True

Question 41

Host inhibitory factors include:

Answer 41

- specific immunity - innate immunity - saliva

Question 42

Which antibody is present in saliva and prevents adhesion?

Answer 42

sIgA (secretory immunoglobin A)

Question 43

Which antibody is present in crevicular fluid and is directed against periodontically important organisms?

Answer 43

IgG

Question 44

The two major salivary proteins are:

Answer 44

- alpha-amylase | - mucins

Question 45

Salivary defenses (minor proteins) include:

Answer 45

- salivary lysozyme - salivary lactoferrin and serum transferrin - Sialoperoxidase system - antimicrobial peptides - acidic proline-rich proteins and statherin

Question 46

What is the function of salivary lysozyme?

Answer 46

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

Question 47

What is the function of salivary lactoferrin and serum transferrin?

Answer 47

They bind iron so that it is not bioavailable to bacteria

Question 48

What is the function of the sialoperoxidase system?

Answer 48

Generates superoxide radicals which inactivate bacterial enzymes leading to bacterial death

Question 49

What do antimicrobial peptides in saliva do?

Answer 49

They have activity against bacteria and yeast

Question 50

What do acidic proline-rich proteins and statherin do?

Answer 50

They modulate salivary calcium and phosphate chemistry

Question 51

What are two mechanisms for maintaining tooth integrity?

Answer 51

- pellicle proteins/salivary minerals | - salivary buffering

Question 52

Which two bacterial products act as nutrients?

Answer 52

- lactic acid (streptococci and veillonella) | - vitamin K3 (made by veillonella and used by P. gingivalis and P. intermedia)

Question 53

What two bacterial products/processes alter the environment?

Answer 53

- carbon dioxide | - removal of oxygen

Question 54

What are two microbial inhibitory factors?

Answer 54

- bacteriocins | - colonization resistance