Required practical 6

Question 1

Aseptic techniques

Question 2

State 6 aseptic techniques

Answer 2

• Wipe down surfaces with antibacterial cleaner, before and after experiment
• Use a bunsen burner in the work space so that the convection currents draw microbes away from culture.
• Flame the wire 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 3

Why is bacteria incubated at 25 degrees

Answer 3

To prevent growth of pathogens, which occurs at higher temperatures

Question 4

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

Answer 4

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

Question 5

What does the zone of inhibition indicate?

Answer 5

It indicates the bacteria killed by the antibiotic.

The larger the zone the more effective the antibiotic.

If an antibiotic has a very little or no zone of inhibition, the bacteria is likely resistant to the antibiotic

Question 6

State the hazarda and precautions of this practical.

Answer 6

Naked flame: keep away from flammable materials tie hair up, wear goggles

Bacteria is biohazard, use disinfect and wash hands, dispose of bacteria safely

Disinfect is flammable, keey away from naked flame.

Question 7

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

Answer 7

To allow oxygen to enter the petri dish, preventing the growth of harmful anaerobic bateria.

Question 8

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

Answer 8

A bar chart of zone of inhibition against antibiotic.