Science Buddies: "Ask an Expert"

Hi,

I tried the zap that zit experiment with E. Coli and salicylic acid, benzoyl peroxide and sulphuric but it didn’t work ? Should I use a different bacteria or different medications ?

Thank you for your help!
Daniyal


Moderator Note: https://www.sciencebuddies.org/science- ... medication

Hello Daniyal,
To help guide you better, could you provide a little more information about what went wrong? For example, was there no zone of inhibition in any of the groups? Did you include a negative control in your experiment?

It is also helpful to keep in mind that benzoyl peroxide has limited activity against Gram-negative organisms, which includes E. coli, so you may not see a clear zone of inhibition with that bacteria.

The bacterium most commonly associated with acne is Propionibacterium acnes. Remember to mention in your findings that experiment was performed using E. coli in place of P. acnes as it is safer and easier to grow.

The zones of inhibition didnt form around any disk. We do have the control it looks the same as the other quadrants. Should we use P. Acne’s and where can we get it from. These meds don’t seem to work against E Coli.

Thank you for your help!

It is available for purchase from
https://www.fishersci.com/shop/products ... 4/23021139
It is categorized as BSL 1 so you should be able to use this in a high school lab. However, I would recommend discussing this with your teacher or school laboratory staff to determine whether it is feasible and permitted under your science fair or institutional safety guidelines.
Make sure you review all Microorganisms safety and precautions:
https://www.sciencebuddies.org/science- ... sms-safety
Also review the prior approval guidelines for your fair
https://www.sciencebuddies.org/science- ... egulations
Looking at the website, P. acne may not be shipped directly to residential addresses. You may have to work with your school to see if it can be shopped there.

Although it is BSL 1, it might be very challenging to grow this bacterium. It is anaerobic and very slow growing. Access to anerobic incubator might be needed.

Other options are to test increasing concentrations (higher than what you used) of salicylic acid, benzoyl peroxide and sulphuric against E. coli.

Bacillus subtilis, another BSL1 bacterium, is another option and is Gram positive like P. acnes.

Good luck,
Anya

I would add to Anya's great suggestions ...

I would recommend discussing this with your teacher or school laboratory staff to determine whether it is feasible and permitted under your science fair or institutional safety guidelines.

You need to contact the science fair review board if you make any changes regarding the bacteria to be tested, including concentrations as well as changes in drug concentrations. For most science fair review boards, their initial approval of your project applies only to the details that you submitted. So any changes will need their approval.

The potential bonus in contacting them is that someone on the review board might have good suggestions for choice of bacteria and/or drug concentrations!

Best of luck with your project!

Madeline