Antiseptics/antibiotics required practical

To describe the practical steps involved in investigating the effect of antiseptics or antibiotics on bacterial growth using agar plates.
To interpret results by measuring the zone of inhibition and calculating its area to compare the effectiveness of different substances.

This topic is for students studying the full biology course only

"Investigate the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition."

Antibiotics are chemicals produced by microorganisms that can kill bacteria.
Different antibiotics work against different bacteria, so it's important to test their effectiveness.
When an antibiotic is placed on agar jelly, it diffuses outwards and can prevent bacterial growth or kill existing bacteria nearby.

Experimental setup

If the radius of the inhibition zone is 8 mm, the area can be calculated as:
Area = 8 x 8 x 3.14 = 201mm²
The larger the inhibition zone, the more effective the antibiotic is at killing or preventing the growth of that specific bacterial species.

Zones of inhibition.

Antibiotics: Chemicals, often produced by microorganisms, that kill or prevent the growth of bacteria.
Agar plate: A Petri dish containing agar gel, used as a solid culture medium for growing microorganisms.
Nutrient agar: A type of agar gel that provides the nutrients needed for bacterial growth.
Aseptic techniques: Procedures used to prevent contamination by unwanted microorganisms during experiments.
Sterilised: Made free from bacteria or other living microorganisms, typically by heat or chemicals.
Inoculating loop: A wire loop used to transfer microorganisms from one place to another.
Incubate: To keep a culture at a specific temperature for a period to allow microbial growth.
Inhibition zone: A clear area around an antiseptic or antibiotic disc on an agar plate where bacteria have not grown.
Diameter: A straight line passing from side to side through the centre of a circle or sphere.
Radius: A straight line from the centre to the circumference of a circle (half the diameter).

Antiseptic vs. Antibiotic Research: Research the difference between antiseptics and antibiotics, including where they are used and why you wouldn't use an antiseptic internally or an antibiotic externally for cleaning surfaces.
Antibiotic Resistance Investigation: Find out what antibiotic resistance is, how it develops, and why it is a major global health concern. You could research specific examples of resistant bacteria.