GI: Investigating Selection

Question 1

How to investigate the effects of antibiotics on bacterial growth?

Answer 1

1. Use sterile pipette to transfer bacteria from broth to agar plate
2. Spread using a sterile inoculating loop
3. Use sterile forceps to place paper discs soaked with different antibiotics - ensure negative control of sterile water
4. Lightly tape lid, invert + incubate at 25^oC for 48 hours
5. Measure size of inhibition zone

Question 2

What aseptic techniques should be used?

Answer 2

1. Disinfect work surfaces and avoid contaminating utensils
2. Sterile equipment
3. Work near Bunsen flame - hot air rises = microbes in air drawn away from culture
4. Minimise time with lid off agar plate
5. Flame neck of container of broth after opening and before closing