Core Practical 9

• What is the purpose of aseptic technique?

  To avoid contamination of the sample
• Why is aseptic technique important for data reliability?

  It ensures reliable and repeatable data
• What are the steps involved in aseptic technique?

  • Wipe surfaces with antibacterial cleaner
  • Use a Bunsen burner to create convection currents
  • Flame the wire hoop before transferring bacteria
  • Flame the neck of bottles before use
  • Minimize time vessels are open
  • Close windows and doors to limit air currents
• What should be used to wipe down surfaces before an experiment?

  Antibacterial cleaner
• How does a Bunsen burner help in aseptic technique?

  It creates convection currents to draw microbes away
• What should be done to the wire hoop before transferring bacteria?

  Flame the wire hoop
• Why is it necessary to flame the neck of bottles before use?

  To prevent bacteria from entering the vessel
• How long should vessels containing bacteria be kept open?

  For the minimum amount of time
• What is the purpose of closing windows and doors during the experiment?

  To limit air currents
• What equipment is needed for the experiment?

  • Agar plate seeded with bacteria
  • Sample of garlic
  • Sample of mint
  • Mortar and pestle
  • Methylated spirit
  • Pipette
  • Paper discs
  • Petri dish
  • Forceps
  • Tape
• What is the first step in the method for the experiment?

  Carry out aseptic techniques
• How much garlic and mint should be crushed for the experiment?

  3g of each
• What should be done after crushing the garlic and mint?

  Shake occasionally with methylated spirit
• What type of pipette should be used to transfer plant extract?

  Sterile pipette
• How long should the paper discs be left to dry?

  10 minutes
• What should be done with the paper disc after it dries?

  Place it onto a petri dish
• Why should the lid of the petri dish be taped lightly?

  To allow oxygen to enter the dish
• At what temperature should the samples be incubated?

  25°C
• Why should samples not be incubated at 37°C?

  It could enable harmful pathogens to grow
• What should be done after the experiment is completed?

  • Sterilize equipment used to handle bacteria
  • Disinfect work surfaces
• How should the diameter of the inhibition zone be measured?

  Without removing the lid from the agar plate
• What is the formula to calculate the area of the inhibition zone?

  Area = $\pi \left(\frac{d}{2}\right)^2$
• Why is it important to note the incubation temperature?

  To prevent harmful bacteria growth
• What are the hazards and safety precautions in the experiment?

  Hazards:

  • Disinfectant: Flammable
  • Biohazard: Contamination risk
  • Naked flame: Fire hazard
  • Methylated spirit: Flammable and toxic

  
  

  Safety Precautions:

  • Keep away from naked flame
  • Use disinfectant and wash hands
  • Tie up long hair
  • Wear gloves and goggles
• What should be done in case of a fire from a naked flame?

  Put out fire and seek assistance
• What is the risk level associated with disinfectant?

  Low
• What should be done if there is a biohazard risk?

  Use disinfectant and seek assistance
• What is the risk level associated with methylated spirit?

  Medium
• How should the results be presented after the experiment?

  • Plot a bar chart of inhibition zone area
  • Include range bars for measurement uncertainty
• What does a larger inhibition zone indicate?

  Better antimicrobial properties of the plant
• What is the conclusion regarding inhibition zones?

  Larger zones kill more bacteria