Culturing microorganisms

• What is the process of growing bacteria in a laboratory called?

  Culturing
• Why do we culture bacteria in a laboratory?

  To investigate disinfectants and antibiotics
• How often can bacteria multiply under optimal conditions?

  Every 20 minutes
• What are the factors affecting the speed of bacterial growth?

  • Temperature: Bacteria grow fastest in warm environments
  • Nutrient availability: Requires a good supply of nutrients
  • Moisture: Grows fastest in moist conditions
  • Oxygen: Some need oxygen, others do not
• How does temperature affect bacterial growth?

  Most bacteria grow fastest in warm environments
• Why is nutrient availability important for bacterial growth?

  Bacteria need nutrients to grow rapidly
• How does moisture influence bacterial growth?

  Most bacteria grow fastest in moist conditions
• What is the role of oxygen in bacterial growth?

  Some bacteria need oxygen, others do not
• The main difference between nutrient broth and agar is that one is liquid and the other is solid.
• What is an example of an aseptic technique for cleaning surfaces?

  Cleaning with disinfectant like alcohol
• Why is it important to wash hands with antiseptic soap before handling microorganisms?

  To prevent contamination of cultures
• What is the purpose of sterilising instruments and solutions before use?

  To destroy all contaminating microorganisms
• How is sterilisation typically achieved?

  By heating objects to destroy microorganisms
• What is a sterile field in microbiology?

  A sterilised area created by a flame's updraft
• How does a Bunsen burner help in creating a sterile field?

  It creates an updraft that minimizes contamination
• What is the maximum temperature for growing bacteria in incubators to prevent harmful pathogens?

  25°C
• Why is 25°C chosen for incubating bacteria?

  It prevents growth of harmful pathogens
• What are aseptic techniques used for?


  Aseptic techniques are a set of procedures used to make sure a culture medium is not contaminated when attempting to culture microorganisms. 
• How is the inoculating loop sterilised before use?

  By placing it in a Bunsen burner flame
• Why is the inoculating loop allowed to cool in the sterile field area?

  To prevent killing the bacterial culture
• What is done after removing the lid from the bacterial culture bottle?

  The neck of the bottle is flamed
• What is the purpose of flaming the neck of the bacterial culture bottle?

  To move air out and prevent contamination
• What is the next step after flaming the neck of the bottle?

  Dipping the sterilised inoculating loop into the culture
• What is done after dipping the inoculating loop into the bacterial culture?

  The neck of the bottle is flamed again
• Why is the Petri dish lid lifted slightly during the procedure?

  To make zig-zag streaks across the agar
• What technique is used to streak the agar in the Petri dish?

  Zig-zag streaks with the inoculating loop
• What is done after making streaks on the agar?

  The Petri dish lid is quickly replaced
• Why is the lid of the Petri dish secured?

  To prevent contamination of the culture
• How should the Petri dish be stored in the incubator?

  Upside down
• What is the maximum temperature in the incubator at schools and colleges?

  25°C
• Why is the maximum temperature set at 25°C in the incubator?

  To prevent the growth of harmful bacteria
• What is done after the Petri dish is stored in the incubator?

  The inoculating loop is sterilised again
• Why are all work surfaces disinfected after the procedure?

  To prevent contamination and ensure safety
• What are agar plates commonly used for?

  Investigating antiseptics or antibiotics on bacteria
• How do scientists test the effectiveness of antiseptics or antibiotics using agar plates?

  By soaking filter paper discs in solutions
• What happens when filter paper discs soaked in antiseptics are placed on agar plates?

  They show how effective the solutions are
• What indicates that bacteria are not affected by the antiseptic or antibiotic?

  Bacterial growth near the paper discs
• What does a clear area surrounding the paper discs signify?

  Bacteria are affected and have died
• What is the term for the clear area around the paper discs?

  Inhibition zone
• How can the size of the inhibition zone be calculated?

  Using the equation: area = $\pi r^2$