Required Practical 2: Culturing Microorganisms

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

  How to prepare uncontaminated bacterial culture and investigate the effect of antibiotics on bacterial growth
• What is the process by which bacteria reproduce?

  Binary fission
• How quickly can bacteria double in number under suitable conditions?

  Every 20 minutes
• What is a nutrient broth solution used for?

  • Provides all nutrients needed for bacteria to grow and divide
  • Appears cloudy due to 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 that has been solidified using a chemical called agar
• Why is it important to avoid contamination when preparing bacterial cultures?

  To prevent unwanted microorganisms from affecting the culture
• What is the first step in preparing a bacterial culture?

  Sterilizing petri dishes, bacterial nutrient broth, and agar
• How do you sterilize an inoculating loop?

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

  The lid is attached using adhesive tape
• At what temperature do we normally incubate bacteria in schools?

  25 degrees Celsius
• Why do we incubate agar plates upside down?

  To prevent moisture from dripping onto the bacteria
• What is the purpose of using a disinfectant solution on the bench before starting the experiment?

  To kill microorganisms that could contaminate the culture
• What is the role of the Bunsen burner flame when opening a sterile agar gel plate?

  It kills bacteria in the air
• What do we place on the agar plate to investigate the effect of antibiotics?

  Sterile filter paper disks containing antibiotics
• What is the area around the antibiotic disc where bacteria do not grow called?

  The zone of inhibition
• How do you calculate the area of the zone of inhibition?

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

  $452.45 \text{ mm}^2$
• What are the key steps in preparing an uncontaminated bacterial culture using aseptic technique?

  1. Sterilize petri dishes and nutrient broth
  2. Sterilize inoculating loop using a flame
  3. Transfer bacteria onto the dish
  4. Seal the dish with adhesive tape
  5. Incubate the agar plate upside down at 25 degrees Celsius
• What are the steps to investigate the effect of antibiotics on bacterial growth?

  1. Clean the bench with disinfectant
  2. Sterilize inoculating loop
  3. Open sterile agar plate near a Bunsen burner
  4. Spread bacteria evenly over the plate
  5. Place antibiotic disks on the plate
  6. Incubate at 25 degrees Celsius
• Where can you find more questions on culturing microorganisms?

  In the vision workbook
• What is the significance of incubating bacteria at 25 degrees Celsius?

  It reduces the chances that harmful bacteria will grow