Protists

• What are the 3 form

  ciliates

  flagellates

  amoebae
• What do prokaryotes include

  Bacteria and Archaea
• What are the cell contents

  nucleus

  ER

  mitochondria

  golgi

  chloroplast

  ribosomes

  cell wall

  cytoplasmic membrane

  cytoskeleton
• What is the role of cytoskeleton

  trafficking organelles
• Describe photoautotrophic

  Algae

  plastids (red, green or golden)

  Green plastids = chloroplasts
• Describe heterotrophic

  Feed on bacteria, fungi and other protists
• Describe mixotrophs

  photosynthesise and eat bacteria, fungi
• How to view

  microscopic count
• advantages of microscopy


  easy / fast
• disadvantage of microscopy

  uses special microscopy counting slide

  doesn't differentiate between live and dead bacteria
• Describe asexual reproduction

  mitosis

  doubling time take hours/days at 37C

  genetically identical but may vary in components
• Advantages of cysts

  Produced under unfavourable conditions

  Highly resistant to heat, drying & radiation

  Very low water content

  Can survive for 20 years in the environment

  Good resistance to antibiotics/disinfectants

  Effective dispersal mechanism•Can be transmitted to others via faeces
• differences to bacteria

  Cell wall in non-motile photosynthetic

  NO Cell wall in

  • heterotrophic
  • mixotrophic
  • motile photosynthetic
• How to deal with osmosis

  contractile vacuole
• Temperature range

  -5 - 20C (psychrophiles)

  15-45C (mesophiles)

  42-80C (thermophile) BUT cut off at 60
• Oxygen levels

  Obligate aerobes (needs O2)

  Obligate anaerobes (No O2)

  potentially microaerophilic (need O2 but tolerated by low concentration)
• where does anaerobic respiration occur

  hydrogenosomes
• where does aerobic respiration

  mitochondria
• where did mitochondria come from originally

  alpha-proteobacterium (hydrogenosome)
• Where did chloroplast come from


  cyanobacterium
• What is the evidence for endosymbiont theory

  –Size of organelle = size of bacterium Unequal distribution in daughter cells –Contain same ribosomes as bacteria

  –They have a double membrane (engulfing mechanism)

  –Phylogeny analysis relates their DNA to their bacterial origin–Have own circular DNA and replicate by binary fission•
• Describe organellar mixotrophy

  selective digestion

  Eat algal cells

  Not digest plastids

  Plastids fix CO2

  Plastids do not encode polymerase

  They need replenishing (die)

  protist can live without the plastids
• Cellular mixotrophy

  Eats algal cells

  no digestion of algal cells

  algae fix CO2

  algae divide in cell (endosymbiosis)

  Can live without
• Constitutive mixotrophs

  Endosymbiotic algae become organelles

  CANNOT live without

  Only seen in flagellates
• Amoebae


  cytoplasmic streaming
• features of amoebae

  1 macronucleus

  aerobic

  heterotrophic (some mixotrophic)

  asexual reproduction (ONLY)

  motile/ non-motile
• Naked amoebae

  Amoeba proteus

  move by cytoplasmic streaming

  produce psuedopodia (surface)

  Feed by direct interception of prey

  raptorial feeding

  No specific ingestion site
• What are the forms of naked amoebae

  Trophozoites (feeding form)

  cysts (resting stage)

  Floating form (stiffened pseudopodia for dispersal)
• Shelled amoebae

   Enclosed in a shell (‘test’)

   Shell can be made of anything

   Intrashellular cytoplasm within test

   Project extrashellular cytoplasm to move and/or feed

   Raptiorial or diffusion feeding

   Can produce cysts
• testate amoebae

  Raptorial

  freshwater, marine and terresterial
• foraminiferans

  Diffusion

  marine

  teste- CaCO3
• diffusion feeding

  Stationary predator captures prey with sticky extrashellular cytoplasm (‘axopodia’)
• Radiolarians


  Diffusion

  Marine

  Test- silica
• heliozoans


  Diffusion

  Freshwater

  Test- silica
• good impacts


  base of food chain

  keep baterial population healthy

  nutrient cycle role
• bad impact


  Mainly amoebae

  evolution of new bacterial pathogens -act as a reservoir
• Microbial loop

  Photoautotrophs -> heterotrophic protozoa (N and P) or Bacteria (DOC - dissolved organic carbon)

  bacteria -> heterotrophic protozoa (N and P)

  heterotrophic protozoa -> metazoa
• feeding leads to remineralisation (have to maintain a C:N:P of 50:10:1)

  Lose c as CO2

  Lose N as NH4

  Lose P as PO4
• Bad impact:

  Amoebae and macrophages share many similarities

  Bacteria use amoebae to practice evading digestion in amoebae, this allows bacteria to evade our immune system
• Stages of infectious disease:

  Reservoir

  transport to host

  adherence and colonisation

  invasion of tissues

  tissue damage