RP: Culturing microorganisms

• Aseptic technique


  • Sterilize petri dishes, bacterial nutrient broth, and agar
  • Transfer bacteria using a sterilized inoculating loop
  • Seal plate with adhesive tape to prevent contamination
  • 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. Spread bacteria evenly on agar plate near Bunsen burner flame

  4. Place sterile filter paper disks containing antibiotics on plate

  5. Incubate plate at 25°C

  6. Measure zone of inhibition around antibiotic disks to calculate area
• Zone of inhibition


  Region where bacteria are not growing around antibiotic disks
• Bacteria can double in number every 20 minutes with enough nutrients and suitable temperature
• Agar gel plates contain nutrient broth solidified with agar, allowing bacterial colonies to form
• Harmful bacteria are less likely to grow at 25°C incubation temperature