Lecture 1: Oral ecology Flashcards
method for bacterial detection
16S sequencing, rDNA gene alignment
how much of the oral cavity bacteria has been cultivated
more than half
how many species of oral bacteria exist?
700 species
how many species of oral bacteria do individuals carry?
100-200 species
what is the study of interrelationships of organisms and their environment?
ecology
What is a niche?
specific combination of conditions that are necessary for the survival of particular organisms (chemical, physical, biological)
where do microorganisms form stable, thick biofilms (plaque)?
non-shedding hard surfaces of teeth
how are periapical and odontogenic infections formed?
invasion of micro-organisms into soft tissue
soft-tissue surfaces to which bacteria adheres:
sulcus, tongue, mucosa, gingiva
hard tissue (supra) to which bacteria adheres:
fissures, proximal surfaces, buccal and lingual enamel surfaces, cementum, restorations, calculus
hard tissue (sub) to which bacteria adheres:
enamel, cementum, restorations, calculus
____ bacteria floats in water
planktonic
Bacteria that causes most dental problems and medical problems are _____, attach to the surface in biofilms
sessile
biofilms are made up of ____and ____ in an ____
adherent microorganisms, extracellular matrix, aqueous enviornment
3 steps of biofilm life cycle
1) attachment 2) growth 3) detachement to seed new biofilm
T/F: biofilms can be formed from one species of bacteria
true
T/F: biofilms normal have many species of bacteria
true
biofilms can include other microorganisms such as:
fungi, algae, protozoa
Once bacteria attach to a surface, they ____
change
biofilm-adaptive genes turn on when:
- bacteria detect surfaces
- bacteria detect each other (quorum)
- signals pass between bacteria
biofilm species co-exist and cooperate through:
- provide nutrients
- remove toxins
- inter and intra cellular signalling
- division of labor (metabolism)
T/F biofilms are fast growing communities that are highly resistant to antibiotics, host defenses, and mechanical disruption
false, slow growing
antibiotic dose to kill biofilm bacteria
1000x
3 mechanisms for biofilm antimicrobial resistance:
1) slow diffusion
2) persister cells alive but metabolicaly inactive survive and repopulate biofilm
3) close proximity and exchange of resistance genes
T/F most oral bacteria is planktonic
false
Saliva is the main precursor for biofilms
false
Biofilms cause oral problems such as:
- caries
- periodontitis
- osteomyelitis
- osteonecrosis secondary to bisphosphonate therapy
T/F: preventing oral biofilms prevents some invasive diseases such as cellulitis
true
6 oral ecologic determinants for biofilm growth
- surface receptors for adherence
- oxygen tension (Eh)
- pH
- nutrients
- host inhibitory factors
- bacterial community interactions
what are surface sites to which bacteria adheres?
- receptor molecules
- direct bacterial interactions
- extracellular matrix
salivary binding promotes adherence by providing ____ or inhibits by ____ and _____
providing binding sites, agglutinating, clearing
components of saliva
- antibodies (aquired immunity)
- salivary agglutinins
- proline- rich glycoproteins
- alpha-amylase
What is the electrical potential or tendency to oxidize or reduce?
oxidation-reduction potential (Eh)
Eh of aerobes?
positive
Eh of anaerobes?
negative
_____ require O2 at atmospheric levels for growth
obligate aerobes
____ can switch between aerobic and anearobic metabolism
facultative anaerobes (facultative aerobes)
____ require low levels of O2
microaerophilic
T/F aerotolerant anaerobes possess anaerobic metabolism but tolerate the presence of O2
true
to which class of microorganism is O2 toxic?
obligate anaerobes (aerophobes)
how is oxygen toxic to obligate anaerobes?
- causes oxidation of membrane lipids and destruction of cell integrity
- causes oxidation of sulfhydryl groups in enzymes resulting in cross-linking and inactivity
which groups in enzymes are effected by oxygen leading to inactivity?
sulfhydryl groups
what 3 enzymes are anaerobes unable to make?
1) superoxide dismutase (SOD)
2) catalase
3) perroxidase
which oxygen products cause damage to cells?
superoxide and peroxide
superoxide dismutase, catalase, and peroxidase ____ oxygen radicals
detoxify
T/F the number of detoxifying enzymes in the cell determines the ability for them to exist in O2 enviroment
false, distribution
older plaque has a ___ Eh
lower
anaerobic species are found in?
sulcus or mature coronal plaque
facultative and microaerophilic specis found in?
supragingival plaque
what species scavanges O2 to provide anaerobic environment for other species (bridge)?
fusobacterium (F. nucleatum)
pH of soft drink
3
pH of fermentation product; lactate
5
pH in mouth ranges from ____ to _____
5 to 7.5 (periodontal pocket)
what are the nutrients of the supragingival environment?
saliva and ingested food
what are the nutrients of the subgingival environment?
crevicular fluid and cells
T/F carbs and aa’s are readily taken up by bacteria
true, low MW
T/F protens and starches (sticky) are readily taken up by bacteria
false, must be retained
nutrients of saliva?
glycoproteins, inorganic salts, aa’s, glucose, vitamins
components of gingival crevicular fluid?
serum proteins, aa’s, glucose, vitamins, hemin, hormones
T/F endogenous nutrients are sufficient for plaque but not sufficient for caries
true, exogenous carbs are needed
what antibody prevents adhesion?
IgA
IgG acts by?
- inhibits colonization (block binding site/agglutingation)
- act as opsonin
- activate complement system
T/F neutrophils, complement proteins of crevicular fluid, and antimicrobial peptids (defensins, histatins, cathelicidins) are considered innate immune defenses?
true
T/F saliva is an innate defense
true
the major salivary protein that digests starches and binds bacteria and mucins is ______
alpha-amylase
salivary _____ digests peptidoglycan in cell wall leading to osmotic disruption and cell death
lysozyme
salivary ____ and ____ sequesters iron
lactoferrin and serum transferrin
what system produces superoxide radicals to inactivate bacterial enzymes?
sialoperoxidase system
T/F antimicrobial peptides have activity against bacteria and yeast
true
____ and ____ modulate salivary calcium and phosphate chemistry
acidic proline-rich proteins and statherin
lactate produced by streps is required by _____
veillonella
veillonella vonverts lactate to _____ to raise pH for acid-sensitive ____
propionate strep
vitamin K3 (menadione) is synthesized by _____ and used by _____ and _____
veillonella parvula, P. gingivalis, P. intermedia
carbon dioxide is generated by _____ and _____
peptostreptococci and eubacteria
carbon dioxide enhances growth of ____ and ____
capnocytophaga and actinomycetemcomitans
_____ removes oxygen to help species like _____ survive
F. nucleatum/periodonticum, taneralla forsythia
T/F strep salivarius produces enocin (bacteriocin) that inhibits S. pyrogenes
true
major oral niches/ecosystems
- supragingival tooth surface and dorsum of tongue
- gingival crevice
