culturing microorganisms (higher bio only)

• What is binary vision?


  It is the process by which prokaryotic organisms like bacteria divide and reproduce.
• How does binary fission differ from mitosis and meiosis?


  Binary fission occurs in prokaryotic cells, while mitosis and meiosis occur in eukaryotic cells.
• What are the main components of a bacterial cell?


  A bacterial cell has a cell wall, cell membrane, cytoplasm, a large circular strand of DNA, and plasmids.
• What is a flagellum in bacteria?


  A flagellum is a tail-like structure that some bacteria use for movement.
• Why is binary fission considered a type of reproduction?


  Because one bacterial cell divides into two, creating two organisms.
• What are the two main steps a bacterial cell must complete before dividing?


  It must grow larger and replicate its genetic material.
• What is the function of plasmids in bacteria?


  Plasmids contain non-essential genes that may be useful in certain situations.
• How does a bacterial cell replicate its DNA before division?


  It replicates its large circular strand of DNA and its plasmids.
• What happens to the large circular strands of DNA during binary fission?


  They move to opposite sides of the cell before division.
• How does the cell wall form during binary fission?


  A new cell wall grows down the middle of the cell, allowing the two halves to separate.
• How quickly can some bacteria divide under optimal conditions?


  Some bacteria can divide every 20 minutes.
• What is the result of bacterial population growth through binary fission?


  The population doubles with each division cycle.
• How do you calculate the number of division cycles in a given time?


  Divide the total time by the mean division time.
• What does mean division time refer to?


  It refers to the average time it takes for a bacterial cell to divide.
• What are the optimal conditions for bacterial growth?


  • Warm temperature
  • Moist environment
  • Plenty of nutrients
• What factors can affect the mean division time of bacteria?


  • Species of bacteria
  • Environmental conditions (temperature, moisture, nutrients)
• how are bacteria grown?


  Bacteria can be grown in a nutrient broth solution or as colonies on an agar gel plate.
• why must Petri dishes and culture media must be sterilised before use


  this will kill any unwanted bacteria in the solution or on the petri dishes.
• Sterilise the inoculating loop, by heating it in the Bunsen burner flame. Leave it to cool. Alternatively, sterilise it in pure alcohol for a few seconds.

  • Reason - kills any unwanted bacteria that are present on the loop.
• Allow the plate to dry then label half of the petri dish containing the media. Invert the plate and store it upside down.


  Reason - The lid stops additional unwanted bacteria in the air from contaminating the plate. Do not fully seal the lid, as this will stop oxygen from reaching the bacterium, and this may encourage harmful anaerobic bacteria to grow.
• Incubate at a maximum temperature of 25°C in schools 


  Reason - this reduces the chance of growing harmful pathogens, which would grow at 37°C in a human body.
• What technique is used to prepare uncontaminated bacterial cultures?

  Aseptic technique
• What is the purpose of using aseptic technique in bacterial culture preparation?


  To avoid contamination of the cultures
• How do bacteria reproduce?


  By binary fission
• Under optimal conditions, how often can bacteria double in number?


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


  To provide nutrients for bacteria to grow and divide
• Why does the nutrient broth appear cloudy?


  Because it contains a very large number of bacteria
• What is an agar gel plate?


  A petri dish containing nutrient broth that has been solidified with agar
• What is the importance of sterilizing petri dishes and nutrient broth?


  To kill any unwanted microorganisms
• How is bacteria typically transferred into a culture?


  Using an inoculating loop
• How is the inoculating loop sterilized before use?


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


  The lid is attached using adhesive tape
• Why is the agar plate placed upside down in the incubator?


  To prevent moisture from dripping onto the bacteria
• 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 the chances of harmful bacteria growing
• What is the purpose of using filter paper disks in the investigation of antibiotics?


  To test the effect of antibiotics on bacterial growth
• What is the zone of inhibition?


  A region where bacteria do not grow around the antibiotic disc
• How do you calculate the area of the zone of inhibition?


  Using the formula: Area = πR²
• If the radius of the zone of inhibition is 12 millimeters, what is the area?


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


  1. Sterilize petri dishes and nutrient broth.
  2. Sterilize the inoculating loop by passing it through a flame.
  3. Transfer bacteria onto the dish using the loop.
  4. Attach the lid with adhesive tape.
  5. Incubate the agar plate upside down at 25 degrees Celsius.