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Investigating the antibacterial properties of plants.
Why do plants produce antibacterial compounds? It protects the plant from bacterial disease.
1. Add nutrient agar with bacteria suspended in it to a Petri dish.
2. Pipette 0.1cm³ of plant extract onto a sterile paper disk and repeat for other plant extracts. Include a control with no extract soaked in ethanol.
3. Place the discs into the agar and then seal the dish so the lid cannot be opened but air can still get in therefore stopping the development of
anaerobic conditions, which encourages harmful bacteria growth.
4. Incubate for 24 hours at 25 degrees. (don't go anywhere near body temperature of 37 degrees as harmful bacteria could grow)
5. Observe the plates without opening them as bacteria could enter/exit.
6. Record the size of the zone of inhibition by measuring the diameter with a ruler. Larger zone of inhibition more effective substance.
CONSTANT VARIABLES: Time and Temperature.
Use aseptic techniques use Virkon on the benches.
Only bin used Petri dishes once they have been autoclaved.
Don't incubate higher than 30 degrees as harmful bacteria could grow.
Plants need water and inorganic ions.
Water is needed for:
Maintaining structural rigidity
Magnesium ions are needed for the production of chlorophyll the pigment needed for photosynthesis.
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