Required Practical 2: Culturing Microorganisms

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

  Preparing uncontaminated bacterial culture
• What is the method used by bacteria to reproduce?

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

  Every 20 minutes
• What does a nutrient broth solution provide for bacteria?

  All nutrients needed to grow and divide
• What does a cloudy nutrient broth indicate?

  A large number of bacteria present
• What is an agar gel plate used for?

  To culture bacteria
• What is agar in the context of bacterial culture?

  A chemical that solidifies nutrient broth
• What is the purpose of sterilizing petri dishes and nutrient broth?

  To kill unwanted microorganisms
• How is bacteria 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 normally 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
• How do you sterilize an inoculation loop before use?

  Pass it through a cool Bunsen burner flame
• Why do we open a sterile agar gel plate near a Bunsen burner flame?

  The flame kills bacteria in the air
• What do we place on the agar plate to test antibiotics?

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

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

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

  452.45 square mm
• What is the value of PI used in calculations?

  3.14
• 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 passing through 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
  3. Open sterile agar plate near Bunsen burner
  4. Spread bacteria evenly over the plate
  5. Place antibiotic disks on the plate
  6. Incubate at 25°C
• What are the key factors to consider when culturing bacteria?

  • Avoid contamination
  • Use sterile equipment
  • Control incubation temperature
  • Monitor growth conditions