Culturing Microorganisms

• 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. Attach lid using adhesive tape to prevent contamination

  4. Incubate at 25 degrees Celsius to reduce growth of harmful bacteria
• Investigating the 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 disks containing antibiotic onto plate

  6. Incubate plate at 25 degrees Celsius

  7. Measure area of zone of inhibition using equation: Area = π x R^2
• Binary fission


  The process by which bacteria reproduce by dividing into two identical cells
• Nutrient broth


  A liquid growth medium that contains all the nutrients bacteria need to grow and divide
• Agar plate


  A petri dish containing a solidified nutrient medium made from agar gel, used to culture bacteria
• Zone of inhibition


  The region around an antibiotic disk where bacteria do not grow, indicating the antibiotic's effectiveness
• Bacteria can double in number every 20 minutes if given enough nutrients and suitable temperature
• Microorganisms such as bacteria and fungi are naturally present in the environment and can easily contaminate bacterial cultures
• Incubating bacteria at 25 degrees Celsius reduces the chances of harmful bacteria growing