Science Buddies: "Ask an Expert"

Hi, I'm a high school student and I need a bit of help in coming up with a specific experiment for science fair.

I'm interested in doing a project on the effect of herbal remedies on bacterial growth but I am not sure how to go about it. What are some herbal remedies I can use that I can easily obtain? Should I just narrow it down to one remedy to base my experiment on, or should I choose several different remedies? Also, what kinds of bacteria should I use to test it against (again, that shouldn't be too difficult to obtain)? Would it be possible to test pharmaceutical drugs as well and compare the results? And once I get all the materials, how would I actually perform the experiment?

Sorry if I'm asking too many questions at once! Any help or guidance would be greatly appreciated.

Thanks!

If you're working with bacteria, you will need to find a lab to work in. This can either be your high school lab (if it has the equipment you need) or a university lab (which will mean you'll have to ask around to see if you can work with a professor).

You can use either a single remedy or multiple remedies, depending on what you want to do with them. A project for a single remedy might be to test the effects of different concentrations of the remedy. Using multiple remedies, on the other hand, would allow you to compare how efficient they are at slowing and stopping bacterial growth.

For the basic procedure, you can grow the bacteria in a liquid culture, then plate the culture on agar plates. Each plate would be spread with one herbal remedy. A very effective remedy would kill all the bacteria, so nothing would grow on the plates, whereas a less effective remedy would grow some bacterial colonies. A control set which had not received a remedy would be used for comparison.

Have you tried looking in local drugstores for herbal remedies?

Good luck!
Sonia

Hi bobette,

Your experiment sounds interesting. I would suggest trying several different herbal remedies. You should be able to a variety of herbal remedies at your local pharmacy or health food store. Some things that come to mind are garlic, echinacea, ginger, gensing and dandelion just to name a few - I am sure you will find many more. As for pharmaceutical drugs, you could try some that are available over the counter that do not require a prescription.

You will want to use bacteria that are non-pathogenic such as E.coli (Gram negative), you may also want to use a Gram positive bacterial strain too. Initially, I would suggest asking your science teacher about obtaining bacteria and agar plates and other supplies that you will need.

An experiment could go something like this:
After obtaining various herbal remedies and preparing them at one or more concetrations, you could add them sterile filter paper discs that are placed onto bacterial cultures (possibly different species) on agar in petri dishes. The cultures would then be allowed to grow in the incubator overnight (or longer), and the following day you could measure area around the filter papers where bacteria did not grow due to inhibition by the herbal remedies. You could use varying or a single concentration of each remedy and compare the size of the zones of inhibition or you could compare inhibition by various remedies on a Gram negative bacterial species versus a Gram positive bacterial species.

Just some ideas for you to think about. I hope this helps. Let us know if you have any more questions.

Good luck.

Mary

Thanks for the ideas, they were really helpful.

Another couple of questions: Does it matter what form the remedies are in (ie. is it necessary to do any extractions or that sort of thing)? And what is the difference between gram positive and gram negative bacteria?

If you are going to add the remedies into the agar, you will need to have them in liquid form. If you are using a filter paper as Mary suggested, you may be able to use a solid remedy. My feeling, however, is that it will be easier for you to measure results if the remedy is, again, in a liquid form. A liquid remedy will also be easier to control-- you can count exactly how many drops you are putting into the agar or onto the filter paper. If you have leaves or flowers, you can either boil or crush them to extract the essence.

Most bacteria are categorized as either Gram-positive or Gram-negative. Gram-positive bacteria stain purple in an iodine dye, whereas Gram-negative bacteria stain pink. The difference is due to differences in the cell wall. Gram-negative bacteria are also more likely to be pathogenic (disease-causing).

Sonia