Microbiology

• Are bacteria prokaryotic or eukaryotic?

  Prokaryotic
• Whats the capsule? 


  Slime coating to evade phagocytosis
• what are pilli 


  Small surface perfusion responsible for binding
• what are the typical bacteria shapes?

  cocci and rods
• whats a chain called

  strep
• what are the way to group bacteria based on grams

  Gram positive and Gram negative - depends on cell structure
• Whats a feature of Gram positive Bacteria

  Thick outer layer of peptidoglycan
• Whats a feature of Gram negative Bacteria

  thin layer of peptidoglycan hidden under outer membrane
• Whats the process of gram staining?

  1. add crystal violet for 30-40s (all cells stain purple)
  2. Add iodine (mordant) fixes stains to gram positive bacteria
  3. Add alcohol to remove violet stain as its not bonded tightly enough
  4. Safranin stains gram negative cells pink
• What colour do gram negative bacteria appear?

  Pink
• What colour do gram-positive bacteria appear?

  Purple
• whats the purpose of a plasmid ?

  • additional circular DNA
• How can plasmids benefit bacteria?

  1. can confer extra genes
  2. Antibiotic resistance
  3. unique metabolism
  4. Virulence to overcome defences (flagella)
• What are endotoxins also known as?

  lipopolysaccharides
• Where are endotoxins found?

  In gram negative cells
• what are lipopolysaccharides composed of?

  Lipid and an O antigen
• what does the o antigen do on endotoxins?

  O antigens bring a strong immune response causing

  • septic shock
  • inflammatory mediators
• What are exotoxins?How?


  A toxin which causes damage to the host

  • by destroying cells
  • disrupting metabolism
• how can exotins be secreted?

  lysis
• What are the different classes of exotoxins?

  1. cell surface active
  2. membrane damaging
  3. intracellular
  4. matrix damaging
• Whats a superantigen? what can it cause?

  systemic over immune response

  • causes TSS - fever, vomitting etc
  • Binds onto immune cells which causes them to be constantly switched one
• what do membrane damaging exotoxins do?

  Form channels in membrane surface

  • so water can leak in and small molecules leak out causing blebbing - cell lyses
• Whats an enzymatically active toxin?

  a membrane damaging exotoxin
• what do enzymatically active toxins do?

  produces phospholipase which destroys lipopolysaccharides which will lyse the cell open causing e.g. gas gangrene
• What are AB toxins ?

  an exotoxin which binds to cells of small intestine and triggers a receptor which opens CFTR pump.

  1. Cholera toxin binds to the A1 protein which is internalised by the B units
  2. Triggers adenylcyclase which triggers cAMP
  3. cAMP binds to CFTR forcing it open
  4. Chloride ions flood out and to retain osmotic balance sodium and water move in
  5. cAMP and CFTR binding is permenant causing perm efflux of water causing severe diarrhoea
• Best way to cure cholera?

  Watefr
• What are antibiotics used for?

  treat bacterial infection
• what are the two types of antibiotics?

  1. Bacteriocidal
  2. Bacteriostatic
• What are the features of Bacteriocidal antibiotics?

  • kill bacterial cells
  • Target cell wall / membrane
• Features of bacteriostatic bacteria?

  Stops bacteria reproduction

  Target protein synthesis

  Bacteria become quiescent and are removed by detoxification
• what are the three main types of plague?

  Bubonic - bubos in lymph nodes

  • Septicemic - blood stream infection
  • Pneumonic - infects lung tissue causing tissue necrosis
• Why are viruses sometimes not classed as an organism

  MRS GREN

  • doesnt have protein synthesis mechanisms so cant reproduce
• 3 basic parts of virus

  • Genetic Material
  • Capsid - protein shell
  • Evelope - lipid coating
• What are the 6 stages of virus replication?

  • Attatchment - binds to specific site on cell
  • Penetration - injects GM
  • Uncoating - removal of envelope and capsid
  • Replication - uses cell replication machinery
  • Assembly - uses cells protein syntheis machinery to assemble new viral particles
  • Release - cell lysis and release of new phage
• Whats the virus effect on host cells?

  • cellular death
  • cell lysis
  • cell cycle suppression
  • induced apoptosis (programmed cell death)
• Whats vaccination?


  Designed to stimulate immune system to develope adaptive immunity to be used in normal encounters with viruses
• What are the 4 methods of vaccination?

  • inactivated
  • attenuated - weakened
  • component - part of the virus
  • mRNA - manmade mRNA causes cells to produce protein from virus
• stages of vaccinaton?

  1. primary response, slow and weak response
  2. memory cells remain
  3. secondary response - fast and strong response using memory cells
• Whats 4 stages of Marburg virus disease ?

  1. incubation - hosting virus but assymptomatic
  2. generalisation - high fever, aches & pains, vomitting
  3. Early Organ Phase - Shortness of breath, conjunctivitus, blood leakage
  4. Late Organ Phase - Convalescent and survival OR develops into a coma, shock and death