Microbiology

• Microbiology

  The study of microscopic living things
• 3 types of microbe

  • Fungi
  • Bacteria
  • Viruses
• Where microbes can be found

  • Soil
  • Water
  • Plants & animals
• Harmful microbes


  Can make us sick (e.g. Flu virus)
• Beneficial microbes


  Gut bacteria provide us with protection
• What microbes require to live

  • Oxygen
  • Nutrients
  • Water
  • Warmth
• 3 main types of microbe

  • Bacteria
  • Fungi
  • Viruses
• fungi

  • May be single- or multi-cellular
  • Reproduce by spores
  • Feed on dead matter (decay
• bacteria

  • Reproduce by dividing in two
  • single celled organism
  • Contain DNA strand , flagellum and capsule
• Viruses

  • Smallest microbe
  • not made of cells
  • contain DNA inside a protein coat
• Pasteur's swan necked flask experiment

  1. Stage 1-3: Nutrient broth poured into flask and boiled to sterilize

  2. Stage 4-5: Broth stayed fresh as microbes got caught in bent neck

  3. Stage 6-7: Broth went cloudy as microbes travelled in from the air through the broken flask
• Pasteur concluded that microbes are found in the air
• Cross-reactivity

  Antibodies produced to defend the body against cowpox also work against smallpox
• Jenner discovered that when you inject people with cowpox they were immune to smallpox</b>
• Pasteur's experiment demonstrating where microbes come from

  1. Boil 50ml broth in beaker

  2. Divide broth equally between 5 boiling tubes

  3. Set up apparatus as shown
• Microbes were already present in the boiling tubes before the experiment, allowing them to grow when nutrient broth was added
• Finding out the conditions microbes need to grow

  1. Collect sterile swab and agar petri dish

  2. Rub swab over test site and onto agar

  3. Seal petri dish and incubate for 1 week
• Sterile conditions


  Ensures no microbes in petri dish at start
• Sealing petri dish


  Stops contamination or microbes entering
• Agar

  Nutrient jelly
• Incubating at 20°C reduces chance of growing harmful pathogens
• Control plate with nothing added disproves spontaneous generation
• Each colony is many bacteria that have arisen from one bacterial cell
• Ways microbes can enter the body

  • Breathed in through mouth/nose
  • Through skin
  • Exchange of body fluids
  • Contaminated food
• Examples of harmful microbes


  • HIV (virus)
  • Cold and flu (virus)
  • Salmonella (bacteria)
  • Chlamydia (bacteria)
  • Athlete's foot (fungus)
• Body's defence mechanisms against microbes

  • Skin as barrier
  • Breathing organs produce mucus
  • White blood cells (lymphocytes and phagocytes)
• Antigen


  Protein marker on microbe that triggers antibody production
• Antibody

  Protein produced by lymphocytes to fight microbes
• It takes time for lymphocytes to produce antibodies, so we can still get sick
• Immunity

  Protection against a disease
• Active immunity

  Antibodies produced by own body
• Passive immunity


  Antibodies received from another source (e.g. breast milk)
• Active immunisation

  Injecting dead/weakened microbes to trigger antibody production
• Passive immunisation


  Directly injecting antibodies
• Memory cells enable faster antibody production on reinfection
• Vaccine

  Contains dead/weakened pathogens to trigger immune response
• Booster injection

  Contains same pathogen to enable more antibody production
• Yeast is a fungus used in bread making
• Bread making with yeast


  Yeast breaks down sugar to release carbon dioxide, making dough rise
• Yeast is used to make alcohol by fermenting sugar