culturing microorganisms

• 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 agar made from?

  Nutrient broth that has solidified
• What is a nutrient broth solution used for?

  To grow and divide bacteria
• Why does the broth appear cloudy?

  It contains a large number of bacteria
• What is an agar gel plate?

  A solid medium for bacterial growth
• What is the purpose of sterilizing petri dishes and nutrient broth?

  To kill unwanted microorganisms
• How is an inoculating loop sterilized?

  By passing it through a flame
• What is done after transferring bacteria onto the dish?

  Attach the lid with adhesive tape
• Why is the agar plate placed upside down in the incubator?

  To prevent moisture from disrupting colonies
• At what temperature do we normally incubate bacteria in schools?

  25 degrees Celsius
• Why do we incubate bacteria at 25 degrees Celsius?

  To reduce harmful bacteria growth
• What is the first step in investigating the effect of antibiotics?

  Clean the bench with disinfectant
• What does the flame do when opening a sterile agar gel plate?

  Kills bacteria in the air
• What is placed on the agar plate to test antibiotics?

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

  Area where bacteria do not grow
• How do you calculate the area of the zone of inhibition?

  Area = $\pi R^2$
• If the radius of the zone of inhibition is 12 mm, what is the area?

  Area = 452.45 mm²
• 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 to the dish
  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
• What should you remember about the required practical on culturing microorganisms?

  • Follow aseptic techniques
  • Measure the zone of inhibition
  • Calculate area using $\pi R^2$