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IOE - microbiology > host microbe interaction > Flashcards

host microbe interaction Flashcards

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Biology 101 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
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2
Q

what is mutualism (belongs to symbiosis)

A
  • mutual benefit

- both partners derive benefits from the association (closest association)

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3
Q

what is commensalism (belongs to symbiosis)

A
  • one member derives benefits

- other is unaffected (least close association)

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4
Q

what is parasitism (belongs to disbiosis)

A
  • one member derives benefits

- other is harmed

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5
Q

in a condition of health what is our relationship with our own microbiome

A
  • tends to be commensalism + mutualism
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6
Q

what is a pathogen

A
  • microbe capable of causing damage to host

- only a minority of microbes are pathogenic

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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

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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)

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9
Q

what are symbionts

A
  • member of resident microbiota conferring benefit to host
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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
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11
Q

what is dybiosis

A

imbalances in resident human microbiota or our response to them (opposite of symbiosis)

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12
Q

when does dysbiosis occur

A
  • when there is a breakdown in homeostasis

- leads to r/ship becoming parasitic

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13
Q

where does pressure to maintain balance in interactions / homeostasis come from

A

host immune system

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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)

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15
Q

which members of the normal oral microbiota considered opportunistic pathogens cause caries

A

S. mutans
Lactobacillus spp
Actinomyces spp.

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16
Q

which members of the normal oral microbiota considered opportunistic pathogens cause periodontal disease

A 
porphyromonas gingivalis
tannerella forsythia
aggregatibacterium
actinomycetemcomitans
spirochaetes
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17
Q

which members of the normal oral microbiota considered opportunistic pathogens cause aspiration pneumonia

A

staphylococcus spp

anaerobes

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18
Q

which members of the normal oral microbiota considered opportunistic pathogens cause infective endocarditis

A

alpha haemolytic streptococci

staphylococcus spp

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19
Q

which members of the normal oral microbiota considered opportunistic pathogens cause abscesses

A

streptoccoci
actinomyces
gram -ve anaerobes

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20
Q

which members of the normal oral microbiota considered opportunistic pathogens cause candidosis

A

candida spp

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21
Q

which 2 types of interactions help maintain homeostasis

A
  • antagonistic

- synergistic

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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
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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
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24
Q

why may homeostasis break down

A
  • ecological stress

- selection of pathogens that predisposes a site to disease

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25
Q

how do bacteria seek nutrients to live

A

1) chemotaxis (movement towards chemical they require)
2) with products from other microbes in the biofilm
3) from biofilms

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26
Q

why is there a complex r/ship between organisms

A
  • 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
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27
Q

what happens to certain bacterial processes (genes / protein expression) depending on availability of nutrients

A

induced or repressed

28
Q

how are nutrients transported into bacterial cells

A
  • passive or facilitated diffusion
  • active transport
  • group translocation
29
Q

which 2 types of nutrients do oral microorganisms rely on for their growth

A

endogenous (from us - saliva, glycoprotein, crevicular fluid, blood)

exogenous (from outside - from diet)

30
Q

which components of saliva may bacteria metabolise

A 
amino acids
peptides + proteins
vitamins
glycoproteins
gases
31
Q

which components of GCF may bacteria metabolise

A

albumin
proteins
glycoproteins
haem

32
Q

which exogenous nutrients are common to consider in oral bacterial metabolism

A
  • 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
Q

sucrose is an exogenous nutrient made of

A

1 glucose

1 fructose

34
Q

in what ways is sucrose metabolised by bacteria

A

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
Q

what does metabolism refer to

A

overall chemical activity that occurs within a cell or organism
these chemical activities are divided into 2 pathways -> catabolism and anabolism

36
Q

catabolism is

A

breakdown or LARGE organic molecules into smaller more manageable ones which bacteria can process further

37
Q

anabolism is

A

BIOSYNTHESIS + construction of molecules from small units

38
Q

which energy source is used by mostly bacteria colonising humans

A

carbon ie sugars (transfer of energy through this process generates wast product)

39
Q

how do bacterial cells use energy from catabolism

A
  • 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
Q

what 2 pathways can oral bacterium metabolism be, describe these

A

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
Q

what is the pathway for glucose during respiration

A 
glucose 
-> (via glycolysis)
pyruvate
->
H2O (in aerobic respiration)
reduced organic/inorganic compound (in anaerobic respiration)
  • product depends on O2 availability
42
Q

why is aerobic respiration the most efficient way of producing energy

A
  • 38 ATP molecules produced from 1 glucose molecule

by electron transport system in mitochondria of eukaryotic cells
+ through membrane / in cytoplasm of prokaryotes

43
Q

what happens in the electron transport system

A
  • 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
Q

why isnt anaerobic respiration an efficient way of producing energy

A
  • only produces 2 ATP molecules per glucose
45
Q

how does fermentation produce ATP (energy form)

A

by substrate level phosphorylation (instead of usual electron transport chain)

46
Q

what is the pathway for glucose in fermentation

A 
glucose
-> (via glycolysis)
pyruvate
->
fermentation end products (depends on the microbe)
47
Q

fermentation ALWAYS occurs

A

anaerobic

48
Q

what is the end product if yeast is the microbe

A

ethanol

CO2

49
Q

what is the equation by which bacteria convert pyruvate to lactic acid in fermentation

A 
glucose
->
fructose bisphosphate
->
2 triose-phosphate
->
2 phosphoglyceric acid
-> (THIS PRODUCES 2 ATP)
2 pyruvic acid
-> 
2 lactic acid
50
Q

list the different fermentation pathways

A 
homolactic acid
heterolactic acid
ethanolic
propionic acid
mixed acid
butanediol
butyric acid
amino acid
methanogenesis
51
Q

what is assaccharolytic metabolism

A
  • degrades compounds other than sugars (proteins) using proteases
  • proteins broken into amino acids or peptides which bacteria can take up
52
Q

how are peptides further broken down in cells

A

intracellular peptidases

- produces amino acids used in anabolic processes

53
Q

what is urea, what happens when it is degraded

A
  • 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
Q

what does the production of ammonia NH3 from urea breakdown counteract

A

sugar of saccharolytic metabolism that produces a strong acid

55
Q

which enzymes are produced by sub-gingival organisms, how do they contribute to tissue damage and formation of periodontal pocket

A
  • hyaluronidase
  • chondroitin sulphatase
  • collagenase
  • by targeting host structural proteins/glycoproteins associated with host epithelium at periodontal sites
56
Q

through which system does bacterial arginine metabolism occur and what is it converted to

A

arginine deiminase system

  • L-citrulline
  • L-omithine
  • carbamoylphosphate
  • CO2
57
Q

why is arginine added to oral care products

A
  • 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
Q

how does nitrogen metabolism by bacteria illustrate mutualism (symbiotic r/ship) between host and oral bacteria

A

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
Q

where do nitrogen compounds go before reappearing in the oral environment

A
  • mouth
  • stomach and intestine (transports it to kidneys + tissues)
  • blood vessel
  • salivary glands
60
Q

which oral bacteria convert nitrate to nitrite

A

streptococci
veillonella
a. naeslundi
a. odontolyticus

61
Q

how is there a food chain in the mouth

A
  • bacteria (ie streptococcus) metabolise sugar producing waste products ie lactic acid
  • waste products used by other organisms
62
Q

what is the r/ship between waste produced by streptococci and veillonella

what is the consequence of this

A 
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
Q

what is an example of a more complex food chain / microbial community

A
  • 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
Q

what are the stages in the formation of plaque

A 
transmission
acquisition
pioneer species (primary colonisers)
succession
increasing species diversity
climax community (eqm)
65
Q

what is the tooth surface coated with and why does this enable pioneer species to colonise

A

salivary pellicle

makes tooth surface more sticky

IOE - microbiology (5 decks)

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