Microbial cultures

• What is the aim of the experiment?

  Investigate antiseptics' effect on bacterial growth
• What equipment is needed for the experiment?

  • Agar plate
  • Heatproof mat
  • Filter paper discs
  • Three antiseptics (e.g., mouthwash, TCP, antiseptic cream)
  • Disinfectant bench spray
  • 1% Virkon disinfectant
  • Antibacterial handwash
  • Forceps
  • Clear tape
  • Hand wash
  • Wax pencil or permanent marker
  • Incubator set to 25°C
• What should be marked on the agar plate?

  Segments, dots, initials, date, bacteria name
• What should you do before handling the agar plate?

  Wash hands with antibacterial handwash
• How should the filter paper discs be prepared?

  Place different antiseptics onto each disc
• How should the lid of the agar plate be positioned when placing discs?

  Lift at an angle carefully
• What temperature should the incubator be set to?

  25°C
• How long should the agar plate be incubated?

  48 hours
• How should the diameter of the clear zones be measured?

  Using a ruler, take two measurements
• What formula is used to calculate the area of the clear zones?

  Area = $\pi r^2$
• How should results be presented after the experiment?

  In a bar chart
• What are the controlled variables in the experiment?

  • Species of bacteria
  • Area of filter paper disc
• What is the purpose of repeating the procedure with different concentrations?

  To investigate the optimum concentration
• What are the sources of error in the experiment?

  • Irregular area of the clear zone
  • Possible contamination
• What safety precautions should be taken when handling Virkon disinfectant?

  Wear safety goggles
• What should be done before and after handling bacteria?

  Wash hands