Bacteria and antibiotics Experiment Precautions - Disposable aprons and gloves Dispose of waste (aprons, paper towel etc) in specified rubbish bag Disinfect benches after experiment is complete Don’t open sealed agar plates when observing results on day 2 Method Part A – Manufactured antibiotics 1. Label the base of an agar plate, around the edge, with the your group name and the name of the bacteria you are using (either S. albus or E. coli, your teacher will advise you) 2. Using a disposable inoculation loop, streak the agar plate with the bacteria using the method below 3. Place the mastring on the agar plate, using the forceps 4. Put the lid on the petrie dish and seal with sticky tape 5. Place in the incubator, lid down Part B – Natural antibiotics Repeat steps above, but rather than a mastring, place several discs of filter paper on the agar plate, soaked with natural antibiotics (eg. honey, tea tree oil, garlic). You will need to write on the base of the plate, which substance is where. Results Without removing the lid, you will use a ruler to measure the ‘zones of inhibition’ around each antibiotic disc. Use the ‘annular radius’ at the measurement you record in the table. Record the results in the table over the page. Antibiotic Zone of inhibition for E. coli (mm) Zone of inhibition for S. albus (mm) Discussion 1. Which antibiotic worked best on E. coli? 2. Which antibiotic worked best on S. albus? 3. What are the benefits of having several antibiotics that can kill a bacterial species?
