Topic 1 Culturing Microorganisms Rp

• Preparing uncontaminated bacterial culture using aseptic technique

  1. Sterilize petri dishes, bacterial nutrient broth, and agar to kill unwanted microorganisms

  2. Transfer bacteria using a sterilized inoculating loop

  3. Seal plate with adhesive tape to prevent contamination

  4. Incubate plate upside down at 25°C to prevent moisture disrupting colonies
• Investigating effect of antibiotics on bacterial growth

  1. Clean bench with disinfectant

  2. Sterilize inoculation loop

  3. Open sterile agar plate near Bunsen burner flame

  4. Use loop to spread chosen bacteria evenly over plate

  5. Place sterile filter paper discs containing antibiotics onto plate

  6. Incubate plate at 25°C for a few days
• Zone of inhibition


  Region where bacteria are not growing around the antibiotic disc
• Calculating area of zone of inhibition


  Area = π x R^2, where R is the radius of the zone of inhibition
• Bacteria can double in number every 20 minutes with enough nutrients and suitable temperature
• Agar gel plates contain nutrient broth that has been solidified using a chemical called agar
• Incubating bacteria at 25°C reduces the chances of harmful bacteria growing