Environmental Conditions Affecting the Oral Microbiota Flashcards
How to bacteria replicate?
Reproduce asexually via binary fission
Briefly describe binary fission
Cells circular DNA replicates
Divison of cytoplasm membrane and cell wall follows
Basically the cell splits into 2 daughter cells
How do viruses replicate?
They dont posses the necessary ‘machinery’ to reproduce on their own so they must latch onto a host cell
This allows viruses to use the host cells own cytoplasmic material to synthesise viral components
They are non-cellular organism
Why are viruses described as being non-cellular
Because they are made of nucleic acids (DNA OR RNA)
This nucleic avis is enveloped
It is non-cellular as it doesn’t have a phospholipid membrane
How do yeast cells replicate?
Budding
This is a form of asexually reproduction where a new organism develops from a bud as cell division occurs at a specific site of that cell
How can we measure growth of cells?
Estimate the increase in:
- The number of cells
- The dry mass (dry weight)
- The cellular constituents (eg the increase in ATP)
How can we measure population size?
- Total counts using microscopy
2. Viable counts using colony forming units
Describe the total count method?
Can do a total count using a microscope and a special glass slide called the counting chambers
These counting chambers lets you count the cells in a chamber using a microscope
You can count the number of cells in a chamber and then estimate the total number of organism in the whole population
What is a downside to the total count method?
It does not discriminate between living and dead cells
What is the viable count method?
Allows for the estimation of the living cells in a population
What do you need to be able to successfully cultivate viruses?
You require a living host cell to support viral replication
You can use eggs, mammillary cell, prokaryotic cells
If bacterial colonies on agar appear identical what does this suggest?
They are the same organisms
If bacterial colonies on agar appear distinct what does this suggest?
They are different species
What are the 4 stages in a bacterial growth curve
- Lag phase
- Log exponential phase
- Stationary phase
- Death/decline phase
What is on the y axis on a bacterial growth curve
Log10 colony forming units (CFU)
When does the growth of micro organism change?
When the environmental factors affecting bacterial growth change
What are some environmental facts that can influence bacterial growth?
Host defences Availability of nutrients Temperature Oxygen/redox potential pH Antimicrobial compounds Oxygen, Ph, metabolic product gradients Depends on the site of the mouth the bacteria may be in
What are the 3 categories microbes can be grouped into depending on their optimum temperature?
- Psychrophiles grow best at 20 degrees
- Mesophiles grow best at 35 degrees
- Thermophiles grow best at 65 degrees
What can the temperature rise to when inflammation occurs and what can this do
Can inverse to 39 degrees and this has an effect on the microbial populations
What are the 5 categories microbes can be grouped into depending on their optimum oxygen concentrations?
Obligate aerobe: they require the precedes of oxygen to survive
Facultative anaerobe: they are able to grow in both the precedes and absence of oxygen
Microaerophile: require some levels of atomospheric oxygen
Aerotolerant anaerobe: The bacteria require the absence of oxygen but can tolerate oxygen
Obligate anaerobe
Require the complete absence of oxygen
What are obligate anaerobes?
They are highly sensitive to oxygen
They generate energy without oxygen
They Require sites with low redox potential
What type of environment is the mouth in regard to oxygen levels?
Quite aerobic environment
What are the 5 reactive oxygen species?
Molecular oxygen is not toxic but its derivatives are: Singlet oxygen Peroxide anion Superoxide anion Hydroxyl free radical
How are the derivatives of oxygen formed?
They are by products of cellular metabolism
What do detoxifying enzymes do?
Detoxuify the derivatives of oxygen making them less toxic
What are the 3 examples of detoxifying enzymes?
- Superoxide dismutase
- Peroxidase
- Catalase
What does Catalase catalyse?
The breakdown of hydrogen peroxide to water and oxygen
What does Superoxide dismutase do?
Breakdown the superoxide anion into hydrogen peroxide and oxygen
What does Peroxidase do?
Catalyses the breakdown of hydrogen peroxide into water
What is the redox potential and what is it symbolised by?
It is the tendency of a solution to take or give up electrons
Symbolised by Eh
Measured in millivolts
What does a high redox potential mean?
It means the solution has a greater tendency to gain electrons and to be reduced
What happens to the redox potential as plaque develops?
The redox potential decreases from 200mV to -141mV in about a week
What happens to the redox potential in the gingival crevice when gingivitis occurs?
The redox potential decreases from 73mV to -48mV this is due to a change in the local conditions (increased temp etc)
What are the 3 categories microbes can be grouped into depending on their optimum pH levels?
Acidophiles: thrive at acidic pH
Neutrophiles: thrive at neutral pH
Alkalophiles: thrive at alkaline pH
What does it mean if an organism is aciduric?
It can survive and grow at low pHs
What process breaks down glucose and what is it broken down into?
Glycolysis is the breakdown of glucose into PYRUVATE
What are the 2 substance pyruvate is broken down into>
If carbohydrates are limited pyruvate breaks down into ACETATE, FORMATE and ETHANOL (heterofermentation)
If carbohydrates are in excess pyruvate breaks down into lactate
(Homofermentation)
What are endogenous nutrients?
Molecules and proteins produced by the host cells and that can be metabolised by microbiota
Give some examples of some endogenous nutrients
Mucin in saliva
GCF components
What are exogenous nutrients?
Molecules and proteins coming from outside the body eg from the food we eat
What happens when endogenous mucin Is metabolised?
Slow rate of acid production causing a small fall in pH
What happens when endogenous GCF Is metabolised?
Causes a rise in pH
What happens when exogenous sucrose Is metabolised?
Rapid rate of acid production causing a terminally low pH (potentially lower than 5)
What is the name of the group of bacteria that grow best at 20 degrees?
Psychrophiles
What does a low redox potential mean?
It means the solution has a greater tendency to lose electrons and to be oxidised
What is heterofermentation?
Breakdown of pyruvate into ACETATE, FORMATE and ETHANOL
This happens when carbohydrates limited
Which enzyme breaks down hydrogen peroxide into water and oxygen
Catalase
What is glycolysis?
The breakdown of glucose into pyruvate
What is the name of the group of bacteria that grow best at 65 degrees?
Thermophiles
Which enzyme breaks down superoxide anions into hydrogen peroxide and oxygen
Superoxide dismutase
What is pyruvate broken down into when carbohydrates are limited
ACETATE, FORMATE and ETHANOL
This process is called heterofermentation
What is the name of the group of bacteria that grow best at 35 degrees?
Mesophiles
Which enzyme breaks down hydrogen peroxide into water
Peroxidase
What is homorofermentation?
Breakdown of pyruvate into lactate
This happens when carbohydrates are in excess
What is it called if an organism can survive and grow at low pHs?
Aciduric
What is pyruvate broken down into when carbohydrate are in excess?
Lactate
This process is called homofermentation
What is the name of the group of bacteria that grow best at 65 degrees?
Thermophiles
Psychrophiles grow best at what temperature?
20 degrees
Obligate aerobe grow best at what oxygen level?
They require the precedes of oxygen to survive
Facultative anaerobe grow best at what oxygen level?
They are able to grow in both the precedes and absence of oxygen
Mesophiles grow best at what temperature?
35 Degrees
Microaerophile grow best at what oxygen level?
require some levels of atmospheric oxygen
Thermophiles grow best at what temperature?
65 Degrees
Aerotolerant anaerobe grow best at what oxygen level?
The bacteria require the absence of oxygen but can tolerate oxygen
Obligate anaerobe grow best at what oxygen level?
Require the complete absence of oxygen
Give examples of micro organisms that favour neutrality?
S. sanguinis Actinomyces naeslundii, Neisseria etc
Give examples of micro organisms that are acidogenic?
S. mutans
Lactobacilli;
(inhibits “health-associated” species)
Give examples of micro organisms that are Alkalophiles?
Porphyromonas gingivalis (implicated in periodontal diseases)
How can we control microbial growth ?
Via knowledge of their:
- physiology and growth
- ecology
- using external chemicals
- using physical agent
Which functions can antibiotics affect to try and kill bacteria?
- Cell wall synthesis
- DNA replication
- Protein synthesis
- Membrane function
- Synthesis of essential metabolites
Which antibiotics affect the cell wall synthesis of bacteria?
Penicillins
Cephalosporins
Vancomycin
Which antibiotics affect the DNA replication and transcription of bacteria?
Quinolones
Rifampin
Which antibiotics affect the protein synthesis of bacteria?
Chloramphenicol
Tetracyclines
Erythromycin
Aminoglycosides
Which antibiotics affect the membrane function of bacteria?
Polymyxin B
Nystatin
Which antibiotics affect the the synthesis of essential metabolites of bacteria?
Trimethoprim
Sulfonamides
Which antibiotic is most commonly used in dentistry and what does it target
Metronidazole
Works against anaerobes
Penicillins affects what part of the bacteria?
Cell wall synthesis
Trimethoprim affects what part of the bacteria?
Synthesis of essential metabolites
Tetracyclines what part of the bacteria?
Protein synthesis
Polymyxin B affects what part of the bacteria?
Membrane function
Vancomycin affects what part of the bacteria?
cell wall synthesis
Chloramphenicol affects what part of the bacteria?
Protein synthesis
Quinolones affects what part of the bacteria?
DNA replication and transcription
Erythromycin affects what part of the bacteria?
Protein synthesis
Cephalosporins affects what part of the bacteria?
Cell wall synthesis
Nystatin affects what part of the bacteria?
Membrane function
Sulfonamides affects what part of the bacteria?
Synthesis of essential metabolites
Aminoglycosides affects what part of the bacteria?
Protein synthesis
Rifampin affects what part of the bacteria?
DNA replication and transcription
How can you control/ preset the build up of micro organism?
Have good hygiene Use mouthwash Fluoride Get Immunised Replacement therapy Use Probiotics Sterilisation Disinfection Pasteurisation
Define sterilisation
complete removal or destruction of all viable organisms (using autoclave or an oven)
How can antibitoics be classified?
By the part of the bacteria they target eg:
- Cell wall synthesis
- DNA replication
- Protein synthesis
- Membrane function
- Synthesis of essential metabolites
