Lecture 01: Ecology Handout Flashcards
new and old ways of detecting a bacterial species
old: microscopy and cultivation
new: 16S sequencing, rDNA gene alignments, and phylogenic trees
how many species are in the oral cavity?
300+ and more than half have not been cultivated
how many species does a single human harbor in their mouth?
100-200
the mouth is an ____ system
open
transient vs true residents in the cavity that grow
- determine whether ppl share a core micro biome
- understanding if changes in micro biome are correlated with changes in human health
- new technology
- addressing ethics, legal, and social aspects made by research
human micro biome project
which do we have more of…. human cells or bacteria
bacteria
what has more DNA variety… human cells or bacteria
bacteria
how is it thought that we get our human oral micro biome?
degree of early contact
- hygiene hypothesis
- dont kiss babies or will speed S. mutans…
study of the interrelationships of organisms and their environment
ecology
specific combo of conditions that are necessary for the survival of a particular organism
niche
(parameters are physical, chemical, and biological)
(different oral sites harbor different bacterial species)
do niches change over time?
yes
- organisms are acquired
- teeth erupt/lost
- pockets/injuries occur
biofilm thickness ____ over time
if its surfaces are cleaned, ______ occurs
- increased
- succesion
soft tissue surfaces which bacteria adhere to
sulcus, tongue, mucosa, gingiva
hard suffices that bacteria adhere to
“dental plaque”
-supra- and sub gingival hard surfaces
bacteria that float in water
planktonic (most bacteria in the mouth ARE NOT this bc they would be swallowed)
many of the bacteria that cause dental problems are ____
sessile (attached to surface in biofilms)
biofilms are made up of what?
- adherent microorganisms
- extracellular matrix in aqueous environment
sticky material that holds the biofilm together
extracellular matrix
biofilm life cycle
- attachement
- growth to mature biofilm community
- detachment of cells to seed new biofilm formation
biofilms are often formed by single/multiple species of bactera
multiple
may also be fungi, algae, and protazoa
once bacteria adhere to a surface, they _____
change
biofilm bacteria behavior is much more _____ than suspended cell behavior bc they live in _____ ____
- complex
- interactive communities (turn on different set of genes)
when are three cases when biofilm-adaptive genes are turned on?
- bacteria detect surfaces
- bacteria detect each other (quorum sensing)
- signals pass btw them
biofilms are stage, ___-growing communitites that are highly resistant to ______, _____ and ______
- slow
- antibiotics
- host defenses
- mechanical disruption
antibiotic doses that kill suspended cells need to be inc as much as ______ to kill biofilm
1000X
3 primary mechanisms for bioflim antimicrobial resistance
- slowing of diffusion
- “persister cells” that repopulate biofilm
- close proximity and exchange of resistance genes
does prevention of oral bioflims have an effect on preventing invasive species?
yes
host sites for adherance
- host surfaces (receptor molecules)
- direct bacterial interactions
- extracellular matrix
promotes adherence by providing binding sites or inhibits by agglutinating and clearing antibodies and other similar things
salivary binding
what are the O2 %’s in :
- air
- closed mouth
- perio pocket
- supragingival plaque
air: 21%
closed mouth: 12-14%
perio pocket: 1-2%
supragingival plaque: 1-20% (depends on plaque age)
electric potetial or tendency to oxidize or reduce (oxygen level)
oxidation-reduction potential (Eh)
- positive Eh aerobes (high O2)
- negative Eh anaerobes (low O2)
require low levels of O2
microaerophilic
have anaerobic metabolism but tolerate the presence of O2
aerotolerant anaerobes
results in oxidation of membrane lipids and destruction of cells integrity and causes oxidation of sulfhydryl groups in enzymes resulting in cross-linking and inactivity
oxygen toxicity
the sensitivity of anaerobes to oxygen is due to the GENETIC inability to make enzymes such as ___, ____, and ____
- superoxidase dismutase
- catalse
- peroxidases
(in their absence, oxygen can damage the cells)
superoxide dismutase, catalse, and peroxidase do what?
detoxify O2 radicals that are generated by living systems in the presence of )2
older plaque has a higher/lower Eh
lower
this bacteria scavenges O2 and help to provide and anaerobic environment for other species
fusobacterium
negative log of the hydrogen concentration
pH
how to affect pH: directly or indirectly
directly: carbonated soft drink
indirectly: bacterial fermentation of sugars)
pH normally ranges from what to what?
5-7.5
low pH inhibits most oral species except for what?
acid tolerant (acid uric) strep and lactobacilli
exogenous (injested) nutrient sources are important for ____ species
supra gingival species
(frequency is important)
- low molecular weight, soluble carbs and amino acids readily taken up by bacteria
- starches and proteins must be retained for bacterial digestion to occur
two nutrient sources for biofilms in the oral cavity
- exogenous (injested)
- endogenous (saliva, shed host cells, GCF)
endogenous nutrients sufficient for _____ but not for _____ (why)
- plaque
- caries
*bc you need carbs to have caries
what are the three host inhibitory factors?
- antibodies
- innate immunity
- saliva
what are the two antibodies associated with host inhibitory factors
-sIgA (in saliva, prevents adhesion)
IgA (in GCF, stops invasion of soft tissues)
most salivary proteins are what two things?
- alpha amylase (digests starches and binds bacteria)
- mucins (lubricants)
what are some of the salivary defenses (minor proteins)
- salivary lysozyme
- salivary lactoferin and transferin
- sialoperoxidase system
- antimicrobial peptides
- acidic proline
produced by metabolism of sugars by streps and is required by Veillonella
lactic acid
carbon dioxide is generated by a number of organisms and does what?
ENHANCES THE GROWTH of AA
what are two examples of microbial inhibitory factors
- bacteriocins
- colonizaiton resistance (established organism occupies the niche preventing new strains)
