Science Buddies: "Ask an Expert"

Hi! My name is Sarah and I'm in 8th grade. I'm testing to see if wheatgrass has any antibacterial/antifungal properties. I already have a method for testing antibacterial properties but I still need a way to test for antifungal properties. Besides this, I have a few other questions:

1) i'm comparing the results of the antibacterial properties in wheatgrass to the results of antibiotics (amoxicillin, erythromicyn, trimethoprim-sulfamethoxazole) and I am testing all 4 substances on 4 different types of bacteria ( staph epi, staph aureus, e. coli, group a strep). I need to identify my independent variable. Would that be the wheatgrass and antibiotics or the types of bacteria?

2) what are the best/easiest fungi to test? would candida or trichophyton be suitable?

in case you don't follow, my whole project technically is made up of 2 smaller experiments: 1. testing for antibacterial properties 2. testing for antifungal properties. thank you in advance!!

Hi Cherry, you can use the Kirby-Bauer disk-diffusion method to measure antibacterial or antifungal property. The zone of inhibition is the critical point where the amount of drug at that distance is unable to inhibit the growth of the organism that you are using. Therefore the larger the zone of inhibition, the more efficient the disinfectant is. For wheat grass you can add a drop of wheatgrass juice on the filter paper, and place it on the plate with bacteria uniformly swabbed across the plate and see whether there is a zone of inhibition. You can check out the following link for instruction:

https://www.sciencebuddies.org/science- ... p014.shtml

For control you can just use a regular filter paper and you will expect bacteria to grow around the paper. You should consult with your teacher to determine what bacteria are safe to use base on the equipments that you have.

Michael

Thanks for the help =) That method is great and really helps me out a lot. I've done some more research on it and I'm using MIC (minimum inhibitory concentration) as my dependent variable/the variable i am measuring. thanks again!