Required Practical 6

Question 1

Examples of aseptic techniques

Answer 1

• wash hands with soap / disinfectant surfaces to kill microbes / prevent contamination
• sterilise pipette
• flame neck of bottle
• Bunsen burner close for upward current
• lift lid of perti dish at angle

Question 2

Describe a method to investigate the effect of antimicrobial substances on microbial growth

Answer 2

• prepare agar using aseptic techniques
• transfer bacteria from broth to agar and spread
• use sterile forceps to place disc soaked in different antimicrobials for the same length of time
• tape lid to place and incubate at 25°
• measure diameter of inhibition zone

Question 3

Why is the lid not sealed completely?

Answer 3

• allows oxygen to enter, preventing growth of anaerobic bacteria
• more likely to be pathogenic / harmful to humans

Question 4

Why are perti dishes incubated upside down?

Answer 4

So condensation drips onto lid rather than agar