Required Practical 2: Culturing Microorganisms (T)

• What technique is used to prepare uncontaminated bacterial cultures?

  Aseptic technique
• What should you be able to describe by the end of the video?

  Preparing uncontaminated cultures and antibiotic effects
• How do bacteria reproduce?

  By binary fission
• Under suitable conditions, how often can bacteria double in number?

  Every 20 minutes
• What is used to grow bacteria in a liquid medium?

  Nutrient broth solution
• Why does the nutrient broth appear cloudy?

  It contains a large number of bacteria
• What is an alternative method to culture bacteria besides nutrient broth?

  Agar gel plates
• What is agar gel made from?

  Nutrient broth solidified with agar
• What is the purpose of sterilizing petri dishes and nutrient broth?

  To kill unwanted microorganisms
• How is bacteria typically transferred into the culture?

  Using an inoculating loop
• How do you sterilize an inoculating loop?

  Pass it through a flame
• Why do we attach the lid of the petri dish with adhesive tape?

  To prevent contamination
• At what temperature do we typically incubate bacteria in schools?

  25 degrees Celsius
• Why is it important to incubate agar plates upside down?

  To prevent moisture from disrupting colonies
• What is the first step in investigating the effect of antibiotics on bacterial growth?

  Clean the bench with disinfectant
• What is the purpose of passing the inoculating loop through a flame?

  To sterilize it
• How do we open a sterile agar gel plate safely?

  Near a Bunsen burner flame
• What do we place on the agar plate to test antibiotics?

  Sterile filter paper disks containing antibiotics
• What is the zone of inhibition?

  Area where bacteria do not grow around antibiotic
• How do we measure the effect of antibiotics?

  By calculating the area of the zone of inhibition
• What is the formula to calculate the area of the zone of inhibition?

  Area = PI × R squared
• If the radius of the zone of inhibition is 12 mm, what is the area?

  452.45 square mm
• Why is it important to avoid contamination when culturing bacteria?

  To ensure accurate experimental results
• What are the steps to prepare an uncontaminated bacterial culture using aseptic technique?

  1. Sterilize petri dishes and nutrient broth
  2. Sterilize inoculating loop by flame
  3. Transfer bacteria using the loop
  4. Attach lid with adhesive tape
  5. Incubate agar plate upside down at 25°C
• What are the steps to investigate the effect of antibiotics on bacterial growth?

  1. Clean bench with disinfectant
  2. Sterilize inoculating loop by flame
  3. Open sterile agar plate near flame
  4. Spread bacteria evenly over the plate
  5. Place antibiotic disks on the plate
  6. Incubate at 25°C and observe results
• What are the key components of a bacterial culture experiment?

  • Nutrient broth or agar gel
  • Aseptic technique to avoid contamination
  • Antibiotic disks for testing
  • Measurement of the zone of inhibition