Oral Ecology Flashcards
what is the new method to detect bacterial species
16S sequencing rDNA gene alignments to construct a phylogenic tree
in mouth how many bacteria have been cultivated
300+
by 16S sequencing how many bacteria have been detected in the oral cavity
700+
each person harbors how many species
100-200
what is the difference between transient and true residents in the oral cavity
transient residents are not always there, detected on occasion
true residents are always there and grow
each of us have more bacterial or human cells?
we have more bacterial cells than human cells
how microbiota has more/ less DNA variety than our human genome
more microbiota DNA variety
what is ecology
the study of the interrelationships of organisms and their environment
what is a niche
a specifici combination of conditions that are necessary for the survival of a particular organism can be physical, chemical, biological parameters
how are non shedding hard surfaces of teeth unique
microbes can form stable thick biofilms known as plaque
how can microbes invade soft tissues
periapical and odontogenic infections
how does oral microbiology change
microbes are acquired and oral structure change from eruption/lost of teeth, pocket formation and injuries
soft tissue to which bacteria adhere include what
sulcus, tongue, mucosa, gingiva
hard surfaces to which bacteria adhere and form biofilm include what
supragingival: fissures, proximal surfaces, buccal/ lingual enamel, restorations, calculus
subgingival: enamel, cementum, restorations, calculus
planktonic means water
bacteria floating in water
sessile bacteria are what
attaches to a surface in biofilms
what are biofilms made up of
adherent microbes and ECM matrix in aqueous environment
what is a sticky material that holds biofilms together
ECM- what bacteria adhere to has channels that allows fluids to flow through
describe the biofilm life cycle
initial attachment, attachment of other microbes growth and development, release of cells to seed new biofilm formation
describe the composition of biofilms
can be single species but more often formed by many species and can include fungi, protozoa and algae
how do microbes behave in a biofilm
microbe behavior much more complex and interactive by microbes turning on different genes
when are biofilm adaptive genes turned on
when bacteria detect surfaces, detect each other through (quorum sensing), signals pass between bacteria
how do multiple species co exist and cooperate
provide nutrients for each other, remove toxins, inter/ intra species signaling, and dividing labor amongst species
how do biofilms last in a host
biofilms are stable, slow growing communities that are highly resistant to antibiotics, host defenses and mechanical disruption
what needs to be done to kills suspended cells in biofilms
antibiotic doses need to be increase as much as 1000 fold to kill biofilm bacteria
disinfection rates are higher for planktonic or biofilm cells
disinfection rates higher for planktonic bacteria! low disinfection when biofilm exists
what are the 3 mechanisms for biofilm antimicrobial resistance
slow diffusion persister cells (alive but metabolically inactive cells) close proximity and exchange of resistance genes
what are biofilms the cause of
caries, periodontitis, osteomyelitis and osteonecrosis (2nd to bisphosphonate therapy)
cellulitis is caused by invasive bacteria concerning biofilms how would you prevent cellulitis
prevent biofilms prevent invasive bacteria from causing invasive diseases such as cellulitis
what are sites for bacterial adherence
host surfaces (receptor molecules), bacterial interactions, ECM
what does salivary binding do
promotes binding by providing binding sites or inhibits by agglutination and clearing
how do saliva inhibit bacterial adherence
Antibodies, salivary agglutinins, proline rich glycoproteins
Alpha amylase
positive Eh is what
for aerobes high oxygen
negative Eh is what
anaerobes low O
obligate aerobes
require O2 for growth
facultative anaerobes
can switch between aerobic and anaerobic metabolism
microaerophilic
require low levels of O2
aerotolerant anaerobes
anaerobic metabolism but tolerates the presence of O2
obligate anaerobes
do NOT use O2, O2 is toxic kills or inhibits growth
what is the mechanism of O2 toxicity
causes oxidation of membrane lipids and destruction of cell integrity, causes oxidation of sulfhydryl groups in enzymes resulting in cross linking inactivity
why are anaerobes sensitive to O2
anaerobes can not make SOD, catalase, or peroxides so oxygen radicals accumulate causing damage to microbe cells
what happens to thick plaque
has lower Eh and shifts to anaerobic microbe
where are anaerobic species often found
O2 protected sites such as sulcus and mature coronal plaque
what is found in supra gingival plaque
facultative and microaerophilic species
what microbe is a bridge species that helps provide an anaerobic environment
Fusobacterium
low pH inhibits most oral species except what
acid tolerant (aciduric) strep and lactobacilli
what are the 3 determinants of caries
bacteria present, a substrate and a vulnerable tooth
nutrient niche in supragingival environment
saliva (endogenous)
food (exogenous)
nutrient niche in subgingival environment
GCF and cells (endogenous)
what are exogenous (ingested) nutrient sources important for
supra gingival microbes, do NOT reach sub gingival
starches and proteins must be retained for bacterial digestion
frequency of ingestion is important!
GCF as a endogenous nutrient source
serum transudate
degree of inflammation influences flow and composition
contains tissue and serum proteins, AAs, glucose, vitamins, hemi, hormones
what is sufficient for plaque
endogenous nutrients
what is needed for caries to occur
Exogenous carbs!
what does sIgA do
in saliva prevents adhesion
what does IgG do in GCF
directed against period microbes systemically and locally produced, inhibits colonization, acts as opsonins, activate complement system
what does a amylase do in saliva
digests starches and binds bacteria
mucins do what
lubricates
what does salivary lysozyme do
digests peptidogycan in cell walls leading to cell death
what does salivary lactoferrin and transferrin do
sequesters iron so bacteria can use it
what does sialoperoxidase system do
generates superoxide radicals which inactive bacterial enzymes
what do antimicrobial peptides do
activity against bacteria and yeast
what do proline rich proteins and statherin modulate
modulate salivary calcium and phosphate chemistry
what maintains integrity of teeth
pellicle proteins/ salivary minerals and salivary buffering
what produces lactic acid and how?
strep produces lactic acid by metabolism of sugars
what does veillonella do to lactate
veillonella converts lactate to propionate raising pH
Vitamin K3 is made by who and used by who
Vitamin K3 is made by Veillonella partial and used by P gingival and P intermedia
who removes oxygen so more fastidious anaerobes such as T forsythia can survive
Fusobacterium nucleatum removes O2
what are some microbial inhibitory factors
bacteriocins and colonization resistance by occupying a niche and preventing establishment of new strains
what are the 6 ecological determinants
adherence, Eh, pH, nutrients, host inhibitory factors, bacterial community interactions
