host microbe interaction Flashcards
1
Q
what is symbiosis
A
- close mutually beneficial r/ship between 2 dissimilar organisms
- relationship between host and associated microbiota in normal healthy conditions
2
Q
what is mutualism (belongs to symbiosis)
A
- mutual benefit
- both partners derive benefits from the association (closest association)
3
Q
what is commensalism (belongs to symbiosis)
A
- one member derives benefits
- other is unaffected (least close association)
4
Q
what is parasitism (belongs to disbiosis)
A
- one member derives benefits
- other is harmed
5
Q
in a condition of health what is our relationship with our own microbiome
A
- tends to be commensalism + mutualism
6
Q
what is a pathogen
A
- microbe capable of causing damage to host
- only a minority of microbes are pathogenic
7
Q
what does it mean if a pathogen is considered virulent
A
cause disease in healthy individuals even in small abundance
ie streptococcus mutans
8
Q
what is an opportunistic pathogen
A
- member of resident microbiota (ie commensals)
- able to cause disease / infection under certain circumstances (ie if immunocompromised)
9
Q
what are symbionts
A
- member of resident microbiota conferring benefit to host
10
Q
what are pathobionts
A
- member of resident microbiota conferring disease when loss of normal balance (dysbiosis) between it + host occurs
- ie if it has been translocated from natural environment into one where it can become pathogenic
11
Q
what is dybiosis
A
imbalances in resident human microbiota or our response to them (opposite of symbiosis)
12
Q
when does dysbiosis occur
A
- when there is a breakdown in homeostasis
- leads to r/ship becoming parasitic
13
Q
where does pressure to maintain balance in interactions / homeostasis come from
A
host immune system
14
Q
what factors can lead to opportunistic infections
A
1) damage to epithelium (bacteria invade usually sterile tissue)
2) presence of foreign body at particular site
3) translocation (of normal microbial community) to another site
4) immunosuppression
5) disruption of normal microbiota
6) unknown precipitating factor (cause change in host microbial dynamics)
7) impairment of host defences by exogenous pathogen (from OUTside our bodies + damage immune system)
15
Q
which members of the normal oral microbiota considered opportunistic pathogens cause caries
A
S. mutans
Lactobacillus spp
Actinomyces spp.
16
Q
which members of the normal oral microbiota considered opportunistic pathogens cause periodontal disease
A
porphyromonas gingivalis tannerella forsythia aggregatibacterium actinomycetemcomitans spirochaetes
17
Q
which members of the normal oral microbiota considered opportunistic pathogens cause aspiration pneumonia
A
staphylococcus spp
anaerobes
18
Q
which members of the normal oral microbiota considered opportunistic pathogens cause infective endocarditis
A
alpha haemolytic streptococci
staphylococcus spp
19
Q
which members of the normal oral microbiota considered opportunistic pathogens cause abscesses
A
streptoccoci
actinomyces
gram -ve anaerobes
20
Q
which members of the normal oral microbiota considered opportunistic pathogens cause candidosis
A
candida spp
21
Q
which 2 types of interactions help maintain homeostasis
A
- antagonistic
- synergistic
22
Q
what are antagonistic relationships
A
- refers to hostility
- certain microbes produce antimicrobial agents (produced by our cells) to compete for resources + habitat
- when these are produced we’re trying to maintain the population of the microbiota at these habitats
- these inhibit and kill most of the bacteria
23
Q
what is synergism
A
- refers to cooperation of things that work together towards a common goal
- components produced by host or microbes (ie glycoproteins)
- these are present as endogenous compounds (produced by OUR cells) and bacteria use them as nutrient source and act in a synergistic way allowing bacteria to proliferate and grow
24
Q
why may homeostasis break down
A
- ecological stress
- selection of pathogens that predisposes a site to disease
25
how do bacteria seek nutrients to live
1) chemotaxis (movement towards chemical they require)
2) with products from other microbes in the biofilm
3) from biofilms
26
why is there a complex r/ship between organisms
- certain organisms require v specific nutrients that we may not produce BUT other organisms ARE able to produce through their metabolism
- so they depend on presence of other species for survival
27
what happens to certain bacterial processes (genes / protein expression) depending on availability of nutrients
induced or repressed
28
how are nutrients transported into bacterial cells
- passive or facilitated diffusion
- active transport
- group translocation
29
which 2 types of nutrients do oral microorganisms rely on for their growth
endogenous (from us - saliva, glycoprotein, crevicular fluid, blood)
exogenous (from outside - from diet)
30
which components of saliva may bacteria metabolise
```
amino acids
peptides + proteins
vitamins
glycoproteins
gases
```
31
which components of GCF may bacteria metabolise
albumin
proteins
glycoproteins
haem
32
which exogenous nutrients are common to consider in oral bacterial metabolism
- fermentable carbs (acid production + polymer synthesis)
- dairy products (milk = casein)
- alternative sweeteners (bulk - sorbitol,xylitol, intense - saccharin) which some bacteria are able to process + metabolise
33
sucrose is an exogenous nutrient made of
1 glucose
| 1 fructose
34
in what ways is sucrose metabolised by bacteria
1) broken down into glucose + fructose to produce lactic acid + energy
2) used to make intracellular polymers (ie glycogen) = storage for fasting
3) used to make extracellular polymers (glucan; mutan - glucosyltransferases + fructan (labile in plaque) - fructosyltransferase) = adhesion or food storage and elements of plaque matrix
35
what does metabolism refer to
overall chemical activity that occurs within a cell or organism
these chemical activities are divided into 2 pathways -> catabolism and anabolism
36
catabolism is
breakdown or LARGE organic molecules into smaller more manageable ones which bacteria can process further
37
anabolism is
BIOSYNTHESIS + construction of molecules from small units
38
which energy source is used by mostly bacteria colonising humans
carbon ie sugars (transfer of energy through this process generates wast product)
39
how do bacterial cells use energy from catabolism
- to move
- to generate heat
- to interact with environment
- can be transferred into anabolism processes for constructing a new material allowing bacteria to further react to a stimulus
- useful for cell division
40
what 2 pathways can oral bacterium metabolism be, describe these
SACCHAROLYTIC (carbon source - sugar as nutrient to process metabolic activity)
= sugars -> acids
ASACCHAROLYTIC (not require sugar but proteins etc)
= proteins; peptides -> acids
both lead to acid production
asaccharolytic exists since bacteria dont always have sugars available in environment to live
41
what is the pathway for glucose during respiration
```
glucose
-> (via glycolysis)
pyruvate
->
H2O (in aerobic respiration)
reduced organic/inorganic compound (in anaerobic respiration)
```
* product depends on O2 availability
42
why is aerobic respiration the most efficient way of producing energy
- 38 ATP molecules produced from 1 glucose molecule
by electron transport system in mitochondria of eukaryotic cells
+ through membrane / in cytoplasm of prokaryotes
43
what happens in the electron transport system
- electron transport phosphorylation uses proton motive force to make ATP
- electrons passed through a series of donor acceptor pairs releasing energy
- in aerobic = O2 molecule is terminal electron acceptor
- in anaerobic = inorganic or organic acceptor (which are reduced as have gained electrons)
- through this process ATP is released
44
why isnt anaerobic respiration an efficient way of producing energy
- only produces 2 ATP molecules per glucose
45
how does fermentation produce ATP (energy form)
by substrate level phosphorylation (instead of usual electron transport chain)
46
what is the pathway for glucose in fermentation
```
glucose
-> (via glycolysis)
pyruvate
->
fermentation end products (depends on the microbe)
```
47
fermentation ALWAYS occurs
anaerobic
48
what is the end product if yeast is the microbe
ethanol
| CO2
49
what is the equation by which bacteria convert pyruvate to lactic acid in fermentation
```
glucose
->
fructose bisphosphate
->
2 triose-phosphate
->
2 phosphoglyceric acid
-> (THIS PRODUCES 2 ATP)
2 pyruvic acid
->
2 lactic acid
```
50
list the different fermentation pathways
```
homolactic acid
heterolactic acid
ethanolic
propionic acid
mixed acid
butanediol
butyric acid
amino acid
methanogenesis
```
51
what is assaccharolytic metabolism
- degrades compounds other than sugars (proteins) using proteases
- proteins broken into amino acids or peptides which bacteria can take up
52
how are peptides further broken down in cells
intracellular peptidases
| - produces amino acids used in anabolic processes
53
what is urea, what happens when it is degraded
- molecule in high conc in saliva
| - degraded by urease enzyme (some bacteria possess) into CO2 and NH3 = slightly inc'd pH in oral environment
54
what does the production of ammonia NH3 from urea breakdown counteract
sugar of saccharolytic metabolism that produces a strong acid
55
which enzymes are produced by sub-gingival organisms, how do they contribute to tissue damage and formation of periodontal pocket
- hyaluronidase
- chondroitin sulphatase
- collagenase
- by targeting host structural proteins/glycoproteins associated with host epithelium at periodontal sites
56
through which system does bacterial arginine metabolism occur and what is it converted to
arginine deiminase system
- L-citrulline
- L-omithine
- carbamoylphosphate
- CO2
57
why is arginine added to oral care products
- in its breakdown NH3 is formed and its protonation forms NH4+ which helps raise pH in biofilm
- increases pH in gingival pockets as gingivalis bacteria + streptococcus can undergo arginine metabolism
58
how does nitrogen metabolism by bacteria illustrate mutualism (symbiotic r/ship) between host and oral bacteria
NO3^- nitrate = enters bloodstream through digestion (green veg etc) + eventually reappears in mouth via salivary glands
- 1/4 of ingested nitrate compounds reappear in oral cavity
- oral bacteria (esp those on dorsum of tongue) produce NITRASE REDUCTASE ENZYME = converts nitrate to nitrite (NO2^-)
- NO2^- provides physiological benefit to host by helping regulate blood flow + pressure
59
where do nitrogen compounds go before reappearing in the oral environment
- mouth
- stomach and intestine (transports it to kidneys + tissues)
- blood vessel
- salivary glands
60
which oral bacteria convert nitrate to nitrite
streptococci
veillonella
a. naeslundi
a. odontolyticus
61
how is there a food chain in the mouth
- bacteria (ie streptococcus) metabolise sugar producing waste products ie lactic acid
- waste products used by other organisms
62
what is the r/ship between waste produced by streptococci and veillonella
what is the consequence of this
```
glucose
-> (by streptococci )
lactate
-> (by veillonella )
acetate + propionate
```
- less caries (acetic + proponic acids = weaker acids than lactic so pH increased)
- faster glycolysis (sugar breakdown)
63
what is an example of a more complex food chain / microbial community
- that of streptococcus actinomyces
- produces
1) lactate
2) formate
3) H2O2
4) succinate
veillonella
- use lactate to form acetate (used by eubacterium) and vitamin K (used by porphyromonas prevotella)
wollinella campylobacter
- use formate and h2o2 making protohaem (used by porphyromonas prevotella which produced H2 used by wollinella)
treponema
- uses succinate
64
what are the stages in the formation of plaque
```
transmission
acquisition
pioneer species (primary colonisers)
succession
increasing species diversity
climax community (eqm)
```
65
what is the tooth surface coated with and why does this enable pioneer species to colonise
salivary pellicle
makes tooth surface more sticky
