Required Practical : Culturing Microorganisms (T)

• What is the purpose of aseptic technique in preparing bacterial cultures?

  Aseptic technique is used to avoid contamination of bacterial cultures.
• What are the steps to prepare uncontaminated bacterial culture using aseptic technique?

  • Sterilize petri dishes and nutrient broth
  • Use an inoculating loop to transfer bacteria
  • Sterilize the inoculating loop before use
  • Attach the lid with adhesive tape
  • Incubate the agar plate upside down at 25 degrees Celsius
• How do bacteria reproduce?

  Bacteria reproduce by binary fission.
• What conditions allow bacteria to double in number every 20 minutes?

  Enough nutrients and suitable temperature
• What is a nutrient broth solution used for?

  • Provides nutrients for bacteria to grow
  • Allows bacteria to divide and reproduce
• What is the purpose of agar gel plates in culturing bacteria?

  • Contain nutrient broth in a jelly form
  • Allow bacteria to grow into visible colonies
• Why is it important to avoid contamination when culturing bacteria?

  To ensure accurate results and prevent unwanted microorganisms
• What is the first step in preventing contamination when preparing bacterial cultures?

  Sterilizing petri dishes and nutrient broth.
• How is an inoculating loop sterilized before use?

  Sterilized by passing it through a flame, such as a Bunsen burner.
• What is the purpose of attaching the lid of the petri dish with adhesive tape?

  • Prevents the lid from falling off
  • Stops unwanted microorganisms from entering
• At what temperature do we typically incubate bacteria in schools?

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

  To prevent moisture from disrupting bacterial colonies
• What is the procedure to investigate the effect of antibiotics on bacterial growth?

  • Clean the bench with disinfectant
  • Sterilize an inoculating loop
  • Open a sterile agar plate near a Bunsen burner
  • Spread bacteria evenly over the plate
  • Place antibiotic disks on the plate
  • Incubate at 25 degrees Celsius
• What is the zone of inhibition?

  The area around an antibiotic disk where bacteria do not grow.
• How can we measure the effect of an antibiotic on bacterial growth?

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

  The area equals $\pi \times R^2,$ where $R$ is the radius.
• If the radius of the zone of inhibition is 12 millimeters, what is the area?

  The area is 452.45 square millimeters.
• What is the value of pi used in calculations?

  • The value of pi is approximately 3.14.
• Why is it important to follow aseptic techniques in experiments involving bacteria?

  To ensure valid results and prevent contamination