RP6 Aseptic Techniques

Question 1

State 6 aseptic techniques

Answer 1

• wipe down surfaces with antibacterial cleaner, before and after experiment
• use Bunsen burner in work space so that convection currents draw microbes away from culture.
• flame wire the hoop before using it to transfer bacteria.
• flame the neck of any bottles before using them to prevent any bacteria entering the vessel.
• keep all vessels containing bacteria open for the minimum amount of time.
• close windows and doors to limit air currents.

Question 2

Why is bacteria incubated at 25°c?

Answer 2

To prevent 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 the inhibition (clear zone) on agar.

Question 4

What does the zone of inhibition indicate?

Answer 4

It indicates the bacteria killed by antibiotics. 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 antibiotics.

Question 5

State the hazards and precautions of this practical/.

Answer 5

• naked flame; keep away from flammable material, tie hair up, wear goggles
• bacteria is a biohazard, use disinfectant and wash hands, dispose of bacteria safely.
• disinfectant is flammable, keep away from naked flame.

Question 6

Why should the lid of the Petri dish not be completely taped?

Answer 6

To allow oxygen to enter the Petri dish, preventing growth of harmful anaerobic bacteria.

Question 7

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

Answer 7

A bar chart of zone inhibition against antibiotics.