Investigation Selection

• What are antimicrobial substances?

  Substances that kill microorganisms
• What is the purpose of investigating antimicrobial substances?

  To see if microbes have evolved resistance
• What are antibiotics designed to kill?

  Bacteria
• How can you investigate the effects of antibiotics on bacterial growth?

  By using aseptic techniques in a controlled method
• What is the method for testing antibiotics on bacteria?

  1. Grow bacteria in liquid broth.
  2. Transfer bacteria to an agar plate.
  3. Place antibiotic-soaked discs on the plate.
  4. Incubate at 25°C for 48 hours.
  5. Measure the inhibition zones.
• What is an inhibition zone?

  A clear patch where bacteria can't grow
• What does a larger inhibition zone indicate?

  The antibiotic is more effective against bacteria
• What is the purpose of aseptic techniques?

  • Prevent contamination of cultures
  • Avoid disease-causing microbes
  • Ensure accurate experimental results
• Why is it important to disinfect work surfaces?

  To minimize contamination
• What should you do with contaminated utensils?

  Place them in a beaker of disinfectant
• How can glassware be sterilized?

  Using an autoclave
• Why should you work near a Bunsen flame?

  To draw away airborne microbes
• What should you minimize when working with agar plates?

  The time with the lid off
• What should you do with the neck of the glass container of broth?

  Flame it briefly after opening and closing
• How can you test antiseptics or disinfectants on microbial growth?

  • Use discs soaked in antiseptics or disinfectants
  • Follow the same method as for antibiotics
  • Measure inhibition zones for effectiveness