A student investigated the antimicrobial properties of three different plant extracts—Garlic (G), Tea Tree (T), and Mint (M)—against a strain of bacteria grown on an agar plate.
After 48 hours of incubation, the student observed the zones of inhibition around the paper discs as shown below:
a.[3]
Describe one aseptic technique the student should have used to prevent contamination of the agar plate when preparing this experiment.
b.[2]
Which plant extract is the most effective? Give a reason for your answer.
c.[4]
Calculate the area of the zone of inhibition for Tea Tree. Use π=3.14\pi = 3.14π=3.14. Give your answer to 1 decimal place and include the unit in your final answer.
d.[1]
Suggest one way the student could improve the reliability of this investigation.