Aseptic Techniques

Question 1

Precautions to prevent contamination of agar jelly plate

Answer 1

-keep lid on at all possible times
-use sterile equipment
-autoclave agar
-wear gloves
-work close to a Bunsen burner flame

Question 2

How does working near a Bunsen flame prevent contamination?

Answer 2

It creates an updraft so no bacteria or microorganisms in the air fall down onto the dish

Question 3

How to determine how effective three different antiseptics were at killing bacteria

Answer 3

Soak one filter disc in antiseptic 1, repeat for with fresh filter disc for antiseptic 2 and 3. Soak fresh filter disc in distilled water and space the
discs out. label the Petri dish and incubate.

Measure radius/diameter and calculate the zone of inhibition around each disc (pi r^2). The antiseptic which killed the most bacteria will have
largest zone.

Work near a Bunsen and keep covered most of the time and wash hands.

Make sure incubation time and temperature is the same and the same volume of antiseptic is used and they are soaked for the same time.

As a control soak a fresh filter disc in water or left dry or use a known substance that kills bacteria