Microbiology Flashcards
Learn about the microbiology section of IOE
1
Q
What is the resident microbiota
A
Complete set of microbes that occupy the healthy body site
2
Q
What is the human microbiome?
A
All the microbes associated with the human body
3
Q
Name 6 areas microbial communities in the body
A
Mouth, Skin, axillary, stomach, UI tract, intestine
4
Q
What is one of the main differences between human microbiota and microbiome?
A
The microbiome contains genetic material as well
5
Q
How man microbes are there in 1ml of saliva?
A
10^8
6
Q
What size are eukaryotes? (Fungi, Protozoa)
A
10-100ųm
7
Q
What size are viruses?
A
50-100nm
8
Q
Why are viruses non cellular? (And still alive)
A
Enveloped by a protein coat, not a phospholipid bilayer so technically not a cell
9
Q
Define Classification
A
Arrangement into taxonomic groups based on similarities or relationships
10
Q
In taxonomy, what is the smallest rank?
A
Strain. -family -genus -species -strain Specific strains will have different genes which e.g. can cause virality
11
Q
What is plaque?
A
The community of microorganisms found on the tooth surface as a biofilm embedded in a matrix of polymers of salivary and bacterial origin
12
Q
Name 6 out of the 8 benefits of the resident microbiota
A
[All 8 are given]
- competitive exclusion of exogenous pathogens
- antagonism of exogenous pathogens
- promotion of normal development of immune system
- promotion of normal human cellular physiology and nutrition
- enhancement of epithelial barrier function
- disease follows dis-regulation or imbalance
- certain bacteria actively modulate immune to prevent chronic over-stimulation
13
Q
Name the 4 main distinct sites for oral colonization
A
Teeth, saliva, mucosal surfaces, Gingival Crevicular Fluid (GCF)
14
Q
What is the name of the process that keeps mucosal colonisation relatively low?
A
Desquamation : the shedding of the outer layer if the epithelium
15
Q
Why can teeth allow plaque to accumulate
A
It is non-shedding, so the colonizing on the surface can remain
16
Q
True or false: on a single tooth, there is more than one environment/conditions for microorganisms
A
True
17
Q
Name two liquids in the mouth that can influence where microorganisms colonise and why.
A
Saliva:
- glyoproteins
- host defenses
- buffering role
GCF:
- serum like exudate
- phagocytic cells
18
Q
What is the temperature of the oral cavity?
A
It remains fairly constant at 30, up to 36°C
19
Q
How does redox potential influence microbiology in the oral cavity?
A
It works as a factor in colonisation, it ifluences the type of organism that will be found at a particular site
20
Q
What is the main immunoglobulin in GCF
A
IgG
21
Q
What is the main immunoglobulin in GCF11
A
IgA
22
Q
True of false: the mouth is a non-selective environment
A
False
23
Q
Define symbiosis
A
Close mutually beneficial relationship between two dissimilar orgnanisms
24
Q
What is mutualism?
A
An association between 2 organisms where both partners derive benefit
25
What is commensalism?
A relationship between 2 dissimilar organisms where one gains benefit, the other is unaffected (no harm done)
26
What is parasitism?
One organisms derives benefit, one is harmed in a relationship between 2 organisms
27
What is a pathogen
A microbe capable of causing disease
28
What is an opportunistic pathogen?
An organism that is a member of the resident oral microbiota that causes infection under certain circumstances
29
Describe dysbiosis
Imbalances in the resident human microbiota, or our responses to them
30
Name 5 out the 7 factors that can lead to opportunistic infection
[All 7 given]
- damage to epithelium
- presence of foreign body
- transfer to other body site
- suppression of immune system
- disruption of normal microbiota
- unknown precipitating factor
- impairment of host defenses by exogenous pathogens
31
Name the 3 bacteria that are involved in caries
- streptococcus mutans
- Lactobacillus spp.
- actinomyces spp.
32
Name the 4 bacteria involved in periodontal disease.
- Porphyromonas gingivalis
- Tannerella forsythia
- Spirochaetes
- Aggregatibacterium actinomycetemcomitans
33
Which 3 bacteria are involved in oral abscesses?
- streptococci
- actinomyces
- gram-negative anaerobes
34
Describe how a bacteria may find nutrients
Chemotaxis (movement of an organisms towards an chemical substance)
35
What is catabolism?
The breakdown of large molecules into smaller, more manageable ones which can be processed
36
What is anabolism?
The biosynthesis and construction of large molecules from small units
37
What do bacteria do when there are no sugars available?
They do Asaccharolytic metabolism, where proteins and peptides are used (broken down)
38
How many ATP are produced for 1 molecule of glucose during fermentation from bacteria?
2
39
Name 3 fermentation pathways.
Homolactic acid, Heterolactic acid, Ethanolic, Propionic, Butanediol, Amino acid
40
In the food chain, streptococcus can metabolize glucose to lactate. What can Veillonella do?
Metabolize lactate into acetate and propionate, turning a strong acid into a week acid leading to less caries
41
What is the first thing onto the tooth to start the biofilm?
The salivary pellicle, which makes the tooth sticky for bacteria to attach
42
What is the name of the group of organisms that are the first to colonise an area (succession)
Pioneer species
43
Name 3 different types of plaque (by location)
Fissure plaque, approximal/supragingival plaque and sub-gingival plaque
44
What is a non-selective media?
The composition of the medium will allow the growth of as many organisms as possible
45
What is a selected media?
A medium which contains nutrients which enhance the growth of specific species and may have nutrients to inhibit growth of unwanted species
46
What is a bacterial cell wall made out of?
Peptidoglycan
47
What is a nucleoid?
The region of a prokaryotic cell which contains the loose, coiled, protein associated, double stranded DNA
48
Roughly how many organisms in the mouth are actually culturable?
About 50%, because the lab cannot replicate/don't know the right conditions and nutrients for some of the organisms to grow in a lab environment
49
How many steps are involved in gram staining?
5
50
What is the first step of gram staining?
Take a sample from a grown colony and make a smear on a glass slide
51
What is the second step of gram staining?
Stain with crystal violet
52
What is the third step of gram staining?
Stain with iodine
53
What is the fourth step of gram staining?
Decolourise with acetone
54
What is the fifth step of gram staining?
Counter-stain with safranin
55
What is the colour for a gram-positive result?
Purple
56
What is the colour for a gram-negative result?
Pink
57
How does gram staining work?
The addition of crystal violet will attach to the cell membrane. Acetone dehydrates the sample, shrinking the peptidoglycan layer, tightening it so the stain is locked. Without a cell wall like this, the outer membrane is degraded and the colour is lost, so it is counter-stained with safranin.
58
Why does the addition of safranin not change the colour of gram-positive bacteria?
As the pink is lighter than the purple, the darker colour will shine through so it will still look purple.
59
What gram result are streptococci?
Positive (purple)
60
What shape is a 'cocci' bacteria?
Circular
61
What shape is a coccobacilli bacterium?
Oval
62
What property is used in haemolyis?
An enzyme that can be produced by certain bacteria than can cause hameloysis (break down blood cells)
63
What medium is used in haemolyis?
Blood agar
64
What is the result of alpha-haemolysis?
The iron in the haemoglobin is oxidized, leading to a green shine on the agar plate with partial lysis
65
What is the result of beta-haemolysis?
The enzymes cause a complete rupture of the red blood cells contained in agar, leading to large zones of clearing
66
What is the result of gamma-haemolysis?
There is no lysis whatsoever
67
True of false: you could use a specific metabolic process (and its outcome) to help determine a colony
True.
68
What gram-stain, shape and haemolyis are the oral streptococci bacterium?
Gram-postive, cocci, Alpha-haemolytic
69
What is the catalase test for identification of a colony?
Cataalse in an enzyme that can hydrolyse hydrogen peroxide into water and oxygen
A negative result means it cannot break down hydrogen peroxide, vice versa for opposite.
70
Are streptococcus catalase negative or positive?
Negative
71
Describe the gram stain and characteristics of:
| Actinomyces
Gram +ve
Branched rods
Common in plaque
Opportunistic pathogens
72
Describe the gram stain and characteristics of:
| Lactobacillus
Gram +ve
Rod
Implicated in advanced caries
73
Describe the gram stain and characteristics of:
| Eubacterium
Gram +ve
Found in plaque
Difficult to grow in a lab
74
Describe the gram stain and characteristics of:
| Neisseria
Gram -ve
Aerobic
Early colonisers of the tooth
75
Describe the gram stain and characteristics of:
| Veillonella
Gram -ve
Coccus
Anaerobic
Utilises lactic acid in plaque
76
Describe the gram stain and characteristics of:
| Treponema
Strictly anaerobic
| Implicated in periodontal disease
77
Describe the gram stain and characteristics of:
| Treponema
Strictly anaerobic
| Implicated in periodontal disease
78
Describe the gram stain and characteristics of:
| Fusobacterium
Gram-ve
Filament
Anaerobic, common in plaque
Bridging organisms (think fuse) in succession
79
How do bacteria divide?
Binary fission
80
Describe the total count method to measure growth
Measure microbes in a given sample (e.g. 1ml of saliva)
Place onto a glass square
Then count the number of cells in server boxes and average
(Microscope version of taking a quadrat)
81
What is a problem with the counting chamber method?
You cannot tell if the cells you are counting are alive or dead
82
How does the viable method for counting bacteria work?
Take e.g. 1ml of saliva, culture it on an agar plate, do a serial dilution (making it more and more dilute each time with a sterile broth/medium) and culture the dilution. Then count the colonies and scale back up again
83
What do you require to culture viruses?
Living host cells to support viral replication
84
Name the 4 phases in bacteria growth curves
Lag, exponential, stationary, death/decline
85
What happens during the lag phase of bacterial growth
The bacteria arent multiplying, still metabolically active, time taken to adjust to surrounding conditions
86
What happens during the log phase of bacterial growth?
The bacteria divide rapidly, doubling each division with the lots of available resources
87
What happens during the stationary phase of bacterial growth?
Nutrients levels decrease, waste products build up. Cell death is equal to cell replication
88
What happens during the death phase of bacterial growth?
Run out of nutrients, increasing toxic waste, more bacteria are dying than are being created by division
89
What is the temperature of the mouth?
35°C, can raise to 39 during infection
90
What are psychrophiles?
Organisms that grow in cold temperatures (optimum is around 20°C)
91
What are mesophiles?
Organisms that can grow in moderate temperatures, with an optimum temperature of around 37°C (think me -> medium)
92
What are thermophiles?
Organisms that can grow in high temperatures, with an optimum of around 70°C (think thermo, as in hot)
93
What are obligate aerobes?
Organisms that only grow in the presence of high concentrations of oxygen
94
What are Facultative anaerobes?
They are tolerant to any kind of O2 concentration, will grow anywhere
95
What is a microaerophile?
An organism that thrive only at just lower than atmospheric concentrations of oxygen
96
What is an aerotolerant anaerobe?
An organism that can tolerate small amounts of oxygen but function without oxygen
97
What are obligate aerobes?
Organisms that require no oxygen at all to survive
98
What redox potentials do anaerobes prefer?
Reduced conditions (low potential)
99
How does plaque redox change over time?
First high because high in oxygen, over a couple days more electrons are gained to the RP decreases, allowing the promotion of more anaerobic bacteria
100
What is the 1st stage of biofilm formation?
Within seconds, a surface gets covered in a film of proteins and glyoproteins (acquired pellicle)
Also called conditioning film
101
What is the 2nd stage of biofilm formation?
Passive transport of microbes to the follicle via the flow of saliva.
102
What is the 3nd stage of biofilm formation?
Reversible stage
| The bacteria are held by very weak, long range forces (e.g. van der Waals, ionic attraction)
103
How thick is the conditioning film, and what is it derived from?
Up to 1um thick
| Mostly from saliva, can also have parts from the GCF and the microbes themselves
104
What is the 4th stage of Biofilm formation?
Irreversible stage
Short range, specific, strong interactions caused by complementary molecules on the bacteria that bind to the proteins on the pellicle
They become the early pioneer colonisers
105
What is the 5th stage of biolfilm formation?
Co-adhesion
Where different microbes bind to the primary colonisers, doesn't have receptors complimentary to pellicle but do to the microbes already attached
106
Why dont the microbes just bind to the saliva proteins that make the pellicle in solution?
When the proteins attach, they unwind/change shape, exposing their binding sites
107
What is the plaque matrix?
Sticky polymers produced by both the host and the bacteria that make up around 30% of the plaque volume
Can have proteins, fructans, glucan, extra cellular DNA
108
Describe 6 functions of the plaque matrix
- protection from the environment and host defenses
- nutritional reserve
- structural support to the biofilm
- interacts with molecules
- water retention
- retards penetration of antimicrobials
109
True of false: all reactions between microbes in the biofilm are synergistic and beneficial.
False
110
True of false: you can have altered gene expression when microbes are in a biofilm
True
111
What is MIC?
Minimum Inhibitory Concentration
| The smallest concentration that inhibits growth (doesn't necessarily kill)
112
What is MBC?
Minimum Bactericidal Concentration
| The minimum concentration needed to kill a bacteria (measure of antimicrobial resistance)
