Science Buddies: "Ask an Expert"

I am planning on doing a project on whether bacteria gains resistance to a antibacterial soap. I will get a sample of bacteria and spread it on nutrient agar with a low concentrion of the soap. The bacteria that remain will be introduced to a higher concentration of soap. I will repeat this cycle 5 times. After the last cycle, I will compare the surviving bacteria with the bacteria that had no exposure to the antibacterial soap. Does this sound like a do-able project?Is a sort of alright project?

Thx, simone7

Hello,

Your project idea seems great! The only thing you may want to change is the concentrations you expose the bacteria to; instead of exposing the remaining bacteria with a higher concentration of soap, use the same concentration as before. Then, just replicate the test using different concentrations to start with.

For more information, read over this similar experiment: https://www.sciencebuddies.org/mentorin ... ?from=Home.

I hope that helps! Feel free to ask any more questions you may have!

Hi,
Thanks for the reply. I was wondering, do you need to have specific types of bacteria because I'm not sure where I could get that. With the remaining bacteria after the first round, how would you move it onto a new dish for the next round?

Thanks, Simone7

Hello,

It is a great project that you started!
For your question about the bacteria, I think the only important thing is that you stay with the same kind of bacteria from the beginning to the end (or you can do the experiment on different kinds of bacteria, to see if there is a difference in how much and how fast they can gain resistance to soap).

Don't worry about finding bacteria: they are everywhere! You even have many in your gut that are actually working for you and helping you digest. Not all bacteria are bad
For your project, I think that just putting your finger on the agar plate should do it (don't wash your hand right before you do it though ). Once colonies have grown, pick one (or several, but independently) that you will be working with, and dilute it in water. Here is a protocol:
For each plate, use a sterile swab to pick up bacterial colonies, swirl the swab in a tube of sterile water (10 ml) to dilute the bacteria. Cover the tube and agitate it.
Dip a sterile swab into the dilute bacterial solution and then swab it gently across the plate. Swab in three directions (120° apart) to insure complete coverage of the plate.

I found the protocol on this webpage, I encourage you to check it as you will find here lots of details on how to handle the bacteria for your project:
https://www.sciencebuddies.org/science- ... p013.shtml

Don't hesitate to let me know if you have any more question!

Heloise

Hi,
Thanks for the reply. Will it be obvious the different colonies that are growing? Also, to dilute the bacteria do you just scrape it of the plate to put it in the tube? After you finish with one round, would you take the bacteria that's left off the plate for the next round? Why do you need to dilute the bacteria? When you have the antibacterial soap do you put it on one of those small paper disks? Sorry for all the questions, I am not quite familiar with this. Thanks for all your help, if there is something I should read (book, website..) that will help answer these questions I would be glad to.

Thanks a lot , Simone

You need to use a micro lab for this project. The bacteria you collect from the agar plate has to be swabbed with a sterile Q-tip and then put in a vortex a tube that spins at a high velocity so that the bacteria is evenly distributed and then you take an innoculating loop to spread it across the sterile agar plate. Additionally to get the bacteria after you treated it with soap,you should notice a zone of inhibition.From this ring of bacteria you should be able to take another sample for you next test. Please refer to the Kirby Bauer Disk method. If you have any questions please let me know.

I just wanted to add that you could talk about how this applies to the medical industry in your conclusion of your paper. (Antibiotics kill 99.9% of what they're supposed to and that .1% leads to resistance, and now they need to come up with new drugs for the resistant form).