REQUIRED PRACTICAL 6

Question 1

State 6 aseptic techniques.

Answer 1

1. Wipe down surfaces.
2. Flame the wire hoop before using it to transfer bacteria.
3. Keep all vessels containing bacteria open for the minimum amount of time.
4. Close windows and doors to limit air currents.
5. Work in a clean area to prevent contamination.
6. Use disinfectant to clean work surfaces.

Question 2

Why is bacteria incubated at 25°C?

Answer 2

To prevent the growth of pathogens (harmful bacteria), which occurs at higher temperatures.

Question 3

How can you compare the effectiveness of different antibiotics applied to the same bacteria?

Answer 3

Measure the diameter and calculate the area of the zone of inhibition (clear zone) on the agar.

Question 4

What does the zone of inhibition indicate?

Answer 4

It indicates the bacteria killed by the antibiotic. The larger the zone, the more effective the antibiotic. If an antibiotic has very little or no zone of inhibition, the bacteria is likely resistant to the antibiotic.

Question 5

State the hazards and precautions of this practical.

Answer 5

1. Naked flame: keep away from flammable materials, tie hair up, wear goggles.
2. Bacteria is a biohazard: use disinfectant and wash hands, dispose of bacteria safely.
3. Disinfectant is flammable: keep away from naked flame.

Question 6

Why should the lid not be completely taped to the petri dish?

Answer 6

Allow oxygen to enter the petri dish and prevent growth of harmful anaerobic bacteria.

Question 7

Describe the graph that can be plotted from the results of this practical.

Answer 7

A bart chart of inhibition zone against antibiotic.