Culturing Microorganisms

• What are microorganisms that can be grown in laboratories?

  Bacteria
• Why must strict safety procedures be followed in laboratories?

  To prevent contamination and ensure reliable results
• What are the two main types of culture media for bacteria?

  • Nutrient broth solution (liquid medium)
  • Agar gel plates (solid medium)
• Why are agar plates commonly used in schools?

  They allow bacteria to form visible colonies
• What do bacteria require for growth?

  • Carbohydrates (for energy)
  • Proteins / Amino acids (for growth)
  • Minerals (for enzyme function)
  • Water (for chemical reactions)
• What is the purpose of aseptic techniques in microbiology?

  To prevent contamination of cultures
• What are key aseptic techniques used in preparing cultures?

  1. Sterilise petri dishes and media
  2. Sterilise inoculating loop
  3. Transfer bacteria to agar plate
  4. Spread bacteria evenly
  5. Seal petri dish lid
  6. Incubate plates upside down
  7. Incubate at 25°C
• Why should petri dishes be incubated upside down?

  To prevent condensation on the agar
• What is the maximum temperature for incubating plates in schools?

  25°C
• What is a common experiment in microbiology involving antibiotics?

  Testing how well they kill bacteria
• What is the method for testing antibiotics or disinfectants?

  1. Prepare agar plate with bacteria
  2. Soak paper discs in antibiotics
  3. Place discs on agar
  4. Seal and incubate at 25°C for 48 hours
  5. Measure clear zone around discs
• What does a larger inhibition zone indicate?

  The antibiotic/disinfectant is more effective
• How is the size of the inhibition zone calculated?

  Using the area of a circle formula
• If a bacterium divides every 20 minutes, how many bacteria are present after 3 hours?

  512
• What factors affect bacterial growth?

  • Temperature
  • Nutrient availability
  • Oxygen levels
  • pH levels
• What is the process by which bacteria reproduce?

  Binary fission
• Why is strict hygiene important when working with bacteria?

  Bacteria can be pathogenic
• What should be used in school experiments regarding bacteria?

  Only non-pathogenic strains
• How should cultures be disposed of safely?

  By autoclaving or using disinfectants