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Flashcards

Microbes & Disease - Lecture 5

Afronewtzz Microbes & Disease Degree English 73 cards

Cards in this deck (73)

  1. 1Define Biofilms.A microbial community forming at a phase boundary.
  2. 2What is meant by a phase boundary?Generally a liquid: solid interphase.
  3. 3List the 7 components of a biofilm.- Bacteria
    - Bacteriophage
    - Fungi
    - Algae
    - Protozoa
    - Environmental debris
    - Host components
  4. 4How many species of bacteria is contained within the oral cavity?> 700 species.
  5. 5What % of the special population of bacteria in the oral cavity cannot be cultured?50%
  6. 6What is characteristic of bacteria in the same biofilm?They often have mechanisms to interact/ communicate with eachother.
  7. 7What are the 6 advantages to living within a biofilm?- Stability from adhesion
    - Nutrients available from EPS.
    - Proximity between bacteria of diverse range is protective & cooperative.
    - Habitat diversity (gradients, surface types etc).
    - Bacteria within biofilm can evade host response.
    - Antimicrobial/ disinfectant/ pollutant/ toxic chemical resistance.
  8. 8What is the EPS of the biofilm?- Exopolysaccharide
    - Produced by bacteria in biofilm
    - Acts as a concentrating, sticky filter
    - Provides nutrients
  9. 9In what ways do biofilms become dangerous in medicine?- Man-made invasion of the body (teeth implants, hip replacements, drips, catheters etc...)
    - If not properly sterilised & inserted into body.
    - Bacteria can colonise the area within biofilms.
    - Difficult to remove as a result
  10. 10Describe why you may get symptomatic inflammation/ disease, but not be able to culture the bacterium?Because when it causes a disease it is contained within a biofilm; still remains difficult to remove and culture rapidly.
  11. 11Give an example whereby a biofilm causes very severe, persistent, and infectious, recurrent disease.- Pseudomonas aeruginosa
    - In lung of cystic fibrosis patient
  12. 12Describe how biofilms can cause infectious emboli. Name disease and bacteria example.- Inflammation of the chambers of the heart.
    - Form a biofilm where the bacteria Streptococci colonise.
    - Biofilm can break off when blood flows past and cause spread of infectious emboli around the body.
    - Infective endocarditis.
  13. 13What is the problem with treating a patient suffering from a disease where biofilms form?Often huge, medically impractical (life threatening) doses of antibiotics are required to treat them.
  14. 14What can antibiotics sometimes initiate?- Induce bacteria to create vast biofilms as a defensive response.
  15. 15What transport limitation does the biofilm have on any microbial agent?Causes the antimicrobial agent to be neutralised in the surface layers of biofilm faster than it diffuses in.
  16. 16What physiological limitation does the biofilm have on antimicrobials?- Nutrient-deprived bacteria in the biofilm are forced into a slow-/ non-growing state.
    - Much less susceptible to antibiotics (since antibiotics tend to kill bacteria by preventing replication).
  17. 17What communication mechanism can be used between bacterial cells of the biofilm to promote antimicrobial resistance?Spreading of resistant phenotypic genes to previously susceptible cells.
  18. 18What are Beta-lactam antibiotics?- Contain beta-lactam ring
    - Used to treat a broad spectrum of Gram -ve and Gram +ve bacteria.
  19. 19What is the effect of the secretion of beta-lactamases by a resistant phenotype in the biofilm?- Breaks open lactam ring in susceptible bacterial cells.
    - Renders the antimicrobial agent harmless to the bacteria within the biofilm.
  20. 20What are 5 structural features of the biofilm?- Spatially & temporally heterogenous.
    - Specific mechanisms for attachment to a surface.
    - Generate extracellular polysaccharide (EPS) for adhesion, protection & for allowing community interactions.
    - Resistance to antimicrobials/ disinfectants.
    - Altered metabolic properties & requirements.
  21. 21Describe the 'initiation' stage of biofilm development?- Motile cells with flagella differentiate into non-motile, matrix-producing cells that stop separating & form chains surrounded by ECM.
  22. 22Describe the Maturity stage of Biofilm development.- Matrix-producing cells sporulate (make spores).
  23. 23Describe the 'senescence' stage of biofilm development.- Some cells secrete small molecules such as d-amino acids and polyamines.
    - These break down ECM and allow bacterial cells to dispense.
    - Bacterial cell's motility is restored and some remain dormant.
  24. 24What is meant by a 'heterogenous' population in a biofilm?- Functionally distinct cell types exist within biofilm.
    - Genetically identical.
    - Their differentiation into a specific phenotype is not terminal and can be altered when environmental conditions change.
  25. 25What is an example of a bacterial species which adopts a biofilm in the soil?- Gram +ve Bacillus subtilis
  26. 26What is a planktonic cell?A cell growing in liquid suspension.
  27. 27What is a sessile cell?A cell attached to a surface or to pre-formed biofilm.
  28. 28How do cells alter their cell type from planktonic to sessile?- Gene expression.
  29. 29When bacterial cells alter their gene expression from planktonic to sessile, what 5 phenotypic factors may be altered?- Morphology
    - Demotilised
    - Growth rate (i.e. alter in metabolism)
    - Signalling
    - Antibiotic & disinfectant tolerance
  30. 30Define 'competent state' of a bacterium.The state of which bacteria are able to take up DNA.
  31. 31What are the 4 things recognition and communication exists in the bacterial world for?- Sexual exchange > conjugation
    - Protecting your niche
    - Combatting host defences
    - Population migration (biofilms)
  32. 32What is Quorum Sensing?- When the bacteria 'sense' a change in population density and respond to it using gene expression.
  33. 33What mechanism/ activation mechanism does Quorum Sensing depend on?The activation of a sensor kinase or response regulator by a small diffusible signal molecule.
  34. 34What is the word used to describe a population which has reached a critical size? How do we know when a population has reached this?- Quorate
    - Bacterial behaviour changes
  35. 35As cell density increases... secretion of this small soluble diffusible signal molecule does what?INCREASES (indicating QUORATE)
  36. 36What happens once the concentration of this small, diffusible signal molecule activates the sensor kinase during Quorum Sensing?- Transcriptional regulation
    - Phenotypic change
  37. 37What structures do Gram -ve bacterium tend to prefer for their Quorum Sensing signal molecules?- N-acylhomoserine lactones
  38. 38Give 3 different types of N-acylhomoserine lactones found in Quorum Sensing of Gram -ve bacteria?2-Alkyl-4-Quinolones
    DSF
    C18-FAME
  39. 39What structures do Gram +ve bacteria prefer for their Quorum Sensing signal molecules?Mostly cyclic, but sometimes lactones.
  40. 40Name 3 different types of signal molecule used in Quorum Sensing of Gram +ve bacteria.Gamma-Butyrolactones
    Cyclic peptides
    CSP-1
  41. 41What is meant by intraspecies communication with respect to Quorum Sensing molecules?Being able to communicate with 'your own kind' through Quorum Sensing.
  42. 42What is meant when it is said that Quorum Sensing molecules have such functional versatility?They interact with...
    - Their own bacterial population
    - Competitor bacteria
    - Eukaryotic host cell function
  43. 43What 3 Staphylococcal infections can be derived from Staphylococci that you know of?- Scalded-skin syndrome
    - Impetigo
    - Medical device associated infections.
  44. 44Describe the different stages of the growth curve with respect to Staphylococcus aureus.EXPONENTIAL PHASE:
    - Low cell density
    - Lots of food/ nutrients
    - Expression of cell surface adhesins to allow the binding of their cells to structures in our bodies.
    > Tissue colonisation
    STATIONARY PHASE:
    - Nutrients run out.
    - Higher cell density.
    - Expression of alpha and delta haemolysins & other degrading enzymes.
    > Tissue destruction for nutrients.
    > Further growth & more movement.
    > Corresponds with RNAIII (ribonuclease) expression.
  45. 45What is the most appropriate time for bacteria to coordinate a virulence response? What allows it to do this?- When population density is high so that the immune system does not detect the bacterium when it does not have support from lots of cells.
    - Quorum sensing measure this density.
  46. 46What does Agr stand for in Staph. aureus and what does it do?- Accessory gene locus.
    - Regulatory cascade in bacteria which when switched on and off carries out particular mechanisms in the cell.
  47. 47When Agr is switched on in Staph. aureus, what virulence factors are released? (6)- Enterotoxins
    - TSST-1 (Toxic Shock Syndrome Toxin-1)
    - Haemolysins
    - ETA/ ETB
    - Proteases
    - Lipases
  48. 48When Agr is switched off in Staph. aureus, what virulence factors are released? (6)- Clumping factors
    - Protein A
    - FnBpA (Fibronectin Binding Protein-A)
    - FnBpB
    - Coagulase
    - Adhesins
  49. 49What are Haemolysins?Cause RBC lysis
  50. 50What are enterotoxins?Cause vomiting in host.
  51. 51What are TSSTs?- Toxic Shock Syndrome Toxins
    - Superantigens
  52. 52What are FnBpA/ B?- Fibronectin- Binding Proteins A/ B
    - Enable Staph. aureus to adhere to host cells.
  53. 53What is Coagulase?Causes blood to clot.
  54. 54What does AIP stand for? What is it?- Auto-inducing peptide.
    - Chemical signalling molecule; involved in Quorum Sensing.
  55. 55What is the role of Histidine kinase (sitting in the membrane of the bacterium) in the AIP signalling cascade of Quorum Sensing?- Act as receptors.
    - Autophosphorylate itself & transfers the phosphate group to response regulator/ RR.
    - Signal sensed
  56. 56What is the role of the Response Regulator in the AIP signalling cascade of Quorum Sensing?- Receives phosphate group from Histidine Kinase.
    - Regulates the expression of the AIP, the Histidine Kinase & the RR genes.
    - Looping cascade.
  57. 57Inside the cytoplasm of the bacterium, what does the expression of the AIP, histidine and the RR genes enhance the expression of? (4)- Virulence genes
    - Competence genes
    - Bacteriocins/ Bacterial antimicrobial peptides.
    - Sporulation
  58. 58What is the name of the histidine kinase in Staph. aureus?AgrC (sits in membrane)
  59. 59Describe Quorum Sensing in Staph. aureus.- Chemical signalling molecule interacts with AgrC.
    - Phosphate on AgrC is transferred to AgrA.
    - AgrA works on 2 pathways > The P2 pathway (signal regulation cascade & exportation of AgrD) & The P3 pathway (controls the regulation of exotoxins and surface proteins).
  60. 60Describe RNA III in Quorum Sensing.- Forms a hairpin molecule when stimulated by phosphorylated AgrA (P3 pathway).
    - Forming thermal translational antisense.
    - RNA III can act as both a +/- regulator of both individual proteins (exoproteins and pleiotrophic regulators) by base pairing with the initiation sites.
  61. 61Describe what is meant by Inter-staphylococcal 'warfare' in Quorum Sensing.- Different strains of S. aureus produce at least one of the different AgrD peptides during Quorum Sensing with AIP.
    - Depending on which AgrD is produced, they can have an inhibitory or activating effect on the signalling cascade.
    - They switch on/ off biofilm formation & virulence factor genes.
  62. 62What happens if: Group I AIP + Group I AIP of 2 bacteria... Secrete 2 x YSTCDFILM?Activation of virulence genes etc...
  63. 63What happens if: Group I AIP + Group II AIP of 2 bacteria... Secrete 2 x YSTCDFILM?Inhibition of virulence factors etc...
  64. 64What happens if: Group I AIP + Group III AIP of 2 bacteria... Secrete 2 x YSTCDFILM?Inhibition of virulence genes etc...
  65. 65What happens if: Group II AIP + Group I AIP of 2 bacteria... Secrete 2 x GVNACSSLF AgrD peptide?Inhibition of virulence genes etc...
  66. 66What happens if: Group II AIP + Group II AIP of 2 bacteria... Secrete 2 x GVNACSSLF AgrD peptide?Activation of virulence genes etc...
  67. 67What happens if: Group II AIP + Group III AIP of 2 bacteria... Secrete 2 x GVNACSSLF AgrD peptide?Inhibition of virulence genes etc...
  68. 68What happens if: Group III AIP + Group I AIP of 2 bacteria... Secrete 2 x YINCDFLL AgrD peptide?Inhibition of virulence gene expression etc...
  69. 69What happens if: Group III AIP + Group II AIP of 2 bacteria... Secrete 2 x YINCDFLL AgrD peptide?Inhibition of virulence gene expression etc...
  70. 70What happens if: Group III AIP + Group III AIP of 2 bacteria... Secrete 2 x YINCDFLL AgrD peptide?Activation of Virulence genes etc...
  71. 71In what way can Quorum sensing be used to eavesdrop on the host during infection? Use an example of a bacteria that does this.- E.coli O157: H7 > QseC (HK)/ QseB (RR) normally senses AI-3 (AIP) in the nm range.
    - BUT, can also sense catecholamines (norepinepinephrin & epinepinephrin) > hormones released when the host is under stress.
    - 'Cross-sensing' can be used to induce the expression of the flagellar, T3SS genes and Shiga toxin genes.
  72. 72What are Catecholamines? Name 2. When are they released/ where by our body?Neurotransmitter hormones.
    Norepinepinephrin
    Epinepinephrin
    Released by the gut & up-regulated during infection.
  73. 73What is meant by 'cross-sensing' in Quorum Sensing?Cross-sensing is when bacteria can use alternative signals/ hormones released by the body, beside AIP, in order to up-regulate and down-regulate the expression of certain genes involved in virulence.

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Biofilms & Quorum Sensing
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