Hypothesis (remember this is given to you in Core Science ISAs)
"Extracts from some plants have properties similar to those of medical antibiotics"
Equipment
- Test tubes which have plant extracts in them
- A Petri dish with nutrient agar with safe bacteria
- Filter paper
- A disc containing an antibiotic
- Forceps
- Bunsen Burner
- Incubator
- Sellotape
- Scissors
- Marker Pen
Method
First of all, you need to sterilise a pair of forceps - this can be done by holding them in a bunsen flame. Take a disc of filter paper (using the forceps) and place it in the test tube containing a plant extract. Shake the test tube to fully coat the filter paper. Now place the filter paper disc onto the agar jelly in the Petri dish. Label the petri dish with the name of the plant extract it contains. Now repeat this process using different plant extracts. Use the same petri dish each time but make sure that there is plenty of space around each filter paper disc.Now add the disc containing the medical antibiotic to the agar in the petri dish. Seal up the petri dish with sellotape and place in the incubator.
After leaving for a day or two, measure the space around each disc where no bacteria are growing.
Variables
Independent Variable : Types of plant extract
Dependent Variable : Measurements of the space around each disc where no bacteria are growing
Control variables : Size of filter paper discs, type of agar (use the same petri dish), time of incubation
Risk Assessment
The risks with this experiment are all to do with handling the bacteria in a safe and sterile way. This is a low risk but you need to make sure that the petri dish remains sealed and that the forceps are well sterilised.
Context
This experiment might be useful to drugs companies or agricultural companies wanting to test which antibiotics are most effective to use as pesticides for different situations