Ecology And Microbial Diversity Flashcards
What are the traditional methods to detect bacterial species?
- Microscopy
- Cultivation
- DNA Methods
What is the problem with microscopy in detecting bacterial species?
Difficult to distinguish similar morphotypes
What are some problems with cultivation in detecting bacterial species?
- Special nutrient requirements
2. Minor and slow growing species overgrown
T/F: Although many bacterial species have not been cultivated, more than half of oral cavity bacterial species have been cultivated.
True
How many species of bacteria are in each persons mouth?
Roughly 200 species
What does it mean that the mouth is an open system?
We have transient species vs true residents of the oral cavity that grow
T/F: Each of us has more human cells than bacterial cells.
FALSE
T/F: The mouth has different niches for various bacteria.
TRUE
Hard surfaces (teeth) have thick biofilms called plaque
Soft tissues are invaded by other organisms
What is a planktonic bacteria?
It floats in water
Most bacteria that cause dental problems are __________, meaning they attache to a surface in biofilms.
Sessile
The sticky material that holds a biofilm together is called the ___________.
extracellular matrix
T/F: Biofilms can include multiple bacteria as well as fungi, algae, and protozoa.
True
What causes bacteria to change and express different genes when in a biofilm?
- React to attached surfaces
- React to other bacteria (quorum sensing)
- Signals pass between bacteria
How do species co-exist and cooperate with each other?
- Provide nutrients for each other
- Remove toxins
- Inter- and intra-species signaling
- Create a “division of labor”
How do species within a biofilm compete with each other?
- Antimicrobial peptides
- Peroxide
- Lactic acid
T/F: Biofilms are slow growing.
True
T/F: Biofilms are resistant to antibiotics, host defenses, and mechanical disruption.
True
T/F: It is appropriate to use antibiotics to fight biofilms.
FALSE
Would need to administer antibiotics in toxic doses to defeat biofilm bacteria
What are the primary mechanisms for biofilm antimicrobial resistance?
- Slowing of diffusion
- Persister cells
- Exchange of resistance genes
What are persister cells?
Alive but metabolically inactive cells meant to survive and repopulate biofilm
T/F: Saliva provides a thick film of defense in the mouth.
False
Thin - only a few microns thick
Why are anaerobes sensitive to oxygen?
They are unable to make enzymes such as superoxide dismutase, catalase or peroxidase.
Without these enzymes oxygen products (superoxide/peroxide) cause damage to the cell.
What specific enzymes allow cells to live in the presence of oxygen?
Superoxide dismutase, catalase, and peroxidase
If an environment has a low Eh, what type of bacteria are likely to be found there?
Anaerobes
Low Eh = low oxygen
What bacteria scavenge O2, providing an anaerobic environment for other bacterial species?
Fusobacterium
What are the two major physical nutrient niches in the oral cavity?
- Supragingival: saliva and food
2. Subgingival: GCF and cells
T/F: Ingested food is a good nutrient source for subgingival bacteria.
FALSE
Supragingival only
Although endogenous nutrients are sufficient for __________, in order for ___________ to develop there must be exogenous carbohydrates.
Plaque; caries
What antibody in the saliva can prevent bacterial adhesion?
sIgA
What antibody in the GCF can help prevent biofilm formation?
IgG
What is the major salivary proteins that help inhibit biofilm formation?
Alpha-amylase and mucins
What are two mechanisms for maintaining the integrity of the tooth?
- Pellicle proteins
2. Salivary buffering
How are streptococci and Veillonella connected in a food chain?
Streptococci make lactic acid which is used by Veillenella to keep the pH high for strep
Which bacteria use the vitamin K3 produced by Veillonella?
P. Gingivalis and p. Intermedia
What bacterial product is generated by a number of organisms to enhance the growth of Capnocytophaga and A.a.?
Carbon dioxide
How do “good” microbes inhibit buildup of the “bad” microbes?
- Inhibitory factors (bacteriocins)
2. Colonize niches before the bad can attach
What are the six ecological determinants of bacterial adhesion and survival?
- Surface receptors
- Oxygen tension (Eh)
- pH
- Nutrients
- Host inhibitory factors
- Bacterial community interactions
