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 of bacterial reproduction discussed?

  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 alternative method to culture bacteria besides nutrient broth?

  Agar gel plates
• What is agar used for in gel plates?

  To solidify nutrient broth into jelly
• 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 is the inoculating loop sterilized before use?

  By passing it through a flame
• Why is the agar plate placed upside down in the incubator?

  To prevent moisture from disrupting colonies
• At what temperature are bacteria typically incubated in schools?

  25 degrees Celsius
• Why is it important to incubate bacteria at 25 degrees Celsius?

  To reduce chances of harmful bacteria growth
• What is the purpose of using a sterile agar gel plate in the investigation?

  To avoid contamination during the experiment
• What is the zone of inhibition?

  Area where bacteria do not grow around antibiotics
• How do you 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
• 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 with 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