The Resident Oral Microbiota Flashcards
What is plaque?
The community of microorganisms found on the tooth surface as biofilm embedded in a matrix of polymer of salivary and bacterial origin
What do you call plaque found on the fissures of teeth?
Fissure plaque
How much bacteria can be in fissure plaque?
1-33 x10^6
1,000,000-33,000,000
What do you call plaque found on the side of the tooth?
Approximal plaque
What do you call plaque found on the gingival of the teeth?
Sub ginigival plaque
How much bacteria can be found in sub gingival plaque?
10^3 - 10^6
Why do plaque found in different sites of the mouth have different characteristics
Because the mouth offers varying conditions at different sites in the mouth so only certain bacterial species can survive in certain environments
How much bacteria can be found in the saliva
Up to 10^9 bacteria per mL
1,000,000,000
How much bacterial can be found on the tongue?
100 bacteria
What was the first thing microbiologist do to identify oral bacteria?
They tried to isolate the microbes and grow them in a liquid or solid medium
Give an example of a solid medium microbiologist may have used to grow microorganisms
Agar (soft solid) where you can subculture bacteria on the surface and they use the nutrients in the agar to grow
How many types of growth media and what are they?
2 types:
- Selective
- Non selective
What is a non selective medium
It contains as many nutrients as possible for microbes to grow
What is a selective medium
Creating an environment for only a specific micro organism to grow
Requires you to do further research on specific microorganisms to see what conditions are favourable to them
Give some examples of non selective medium
Blood agar has horse and/ or sheep blood
Give some examples of deceive mediums
Mitis salivarius bacitracin agar allows only mutants streptococcus to grow
Sabouraud agar only allows yeast to grow
What determines the gram reaction of bacteria
Its cell wall
What is the cell wall of bacterial made of?
peptidoglycan
What is the main difference between prokaryotes and eukaryotes
Prokaryotes don’t have a nucleus so their generic material just floats around as plasmids in the cell
What is the DNA coiled into in bacteria
A circular double stranded nucleoid
What is the cytoplasm
A viscous substance that fills in the entirety of the cell and it is packed with ribosomes
What is a flagellum
A tail like extension on some bacteria
How can we identify different bacteria?
Using differential characteristics like: Gram stains Morphology Haemolysis Pigment Metabolic activity Antigens Cellular composition Nucleic acid
Why are not all bacteria cultivable in a lab
Because we are unable to reproduce the unique requirements that each bacterial species may have to grow and multiply
Approximately how many oral bacteria species are we capable of growing in the lab?
70%
What do all bacteria have
A plasma membrane surrounded by a cell wall made up of peptidoglycan
What does it mean if a bacteria is described as being gram-positive
The peptidoglycan on the outside of the cell wall is very thick
There are lipoteichoic acids that transverse and anchor into the membrane
What does it mean if a bacteria is described as being gram-negative
They have a thinner peptidoglycan layer on the outside of their cell wall
It has a second phospholipid bilayer on the outside of the peptidoglycan later
This second phospholipid bilayer has lipopolysaccharides (O antigens) and lipid A which are very unique to the gram negative
What do lipopolysaccharides (O antigens) and lipid A do?
They are recognised by host cells and may be involved in triggering the defence mechanisms and triggering inflammation
Describe how you would carry out gram staining
- You’d take a sample of a colony using a serile loop and you make a smear on a glass slide
- You let that dry using a Bunsen layer
- The heat fixates the cells into the glass slide 4. Use a crystal violet dye to flood that glass slide for a minute
5 Rinse - Then use iodine which will foxate the crystal violet within the peptidoglycan layer
- Decolorisation using acetone (or any type of alcohol)
- Add a counter stain (usually safranin) that will should stain everything pink
Gram positive cells: will be purple
Gram negative cells: will be pink
What result will a gram positive bacteria give during gram staining and at what stage?
A gram positive cell will go purple when alcohol (like acetone) is added
This is because the iodine will have fixated the crystal violet into the peptidoglycan and so the acetone will not decolorise the sample