Science Buddies: "Ask an Expert"

Hi!
I am doing a project for school, and since I got a late start, my teacher pushed back the due date a little. But the preliminary data is due in 4 days, and I need to sign out my teacher's lab and equipment, and in order to do that, I need my materials!
So here's my question: What natural bacterial killers are there? As in, what makes, say, oak leaves less open to infection than maples? If no one knows, I'll be happy with some plants/herbs that are bacteria resistant, too.
Thanks!

Hi Anna,

There are tons of natural antibacterials, so it really depends on what sort of experiment you want to do. In terms of antibacterials made from plants and animals, our bodies make all sorts of proteins with antibacterial properties, but getting them for an experiment might be trickier.

Several more easily obtained chemicals with antibacterial properties include honey, and some essential oils including thyme oil and tea tree oil (as well as others, you can do more research on this), also acids like lemon and vinegar can kill bacteria, and I believe witch hazel has been reported to be antibacterial as well. Capsaicin (the chemical that makes chile peppers hot) has also been reported to have some antimicrobial properties.

In the end, it really depends on what you are planning to test. I'm attaching a pdf that is a review on various plant products that have antimicrobial properties. Many of them may be difficult for you to acquire in their pure form.

Also, here is a link to a website that lists some common plants that are believed to have antimicrobial properties. Make sure to read the disclaimer at the top. These are plants that have widely been claimed to be antimicrobial. They were not necessarily all tested scientifically, but that may make them interesting plants to test in your own scientific experiment. http://www2.hawaii.edu/~johnb/micro/m14 ... 0.8.3.html

I hope this information gives you some ideas, and if you have an idea of what experiment you would like to perform, please post back with those details and we can help you with more detailed information.

Good luck!
JMP

Hi Anna,

This is a great project idea. Here is some information to help you get started.

This is a project idea centered around natural antimicrobial agents: https://www.sciencebuddies.org/science- ... p022.shtml

You could test different natural substances for their antibiotic properties using zones of inhibition,with the procedure described in this project: https://www.sciencebuddies.org/science- ... p014.shtml

Be sure to consult the Microbiology Techniques & Troubleshooting Guide as you decide on your procedure: https://www.sciencebuddies.org/science- ... ques.shtml

Also make sure you read the Microorganisms Safety Guide: https://www.sciencebuddies.org/science- ... fety.shtml

I hope this helps. Please post again (in this same thread) if you have more questions.

Best,
Heather

Wow, thanks for replying to my question!
I was wondering what was the difference between an essential oil and a 'pure form', like JMP said. Does it make a difference? Also, if I have fresh garlic/onions or what-have-you, could I just crush it and use the juices?
And, yes, I was planning on doing the zones of inhibition. How many times would I need to test each antibacterial? How much E. Coli would I need?
Thanks!
Edit*
Also, how exactly would I change the ratios of the liquids that I would be testing? How do I know the ratio to begin with (say, if I bought it in a bottle)?

Hi Anna,

When JMP mentioned the 'pure form,' the reference was to plant products. Here is the Wikipedia article regarding essential oils: http://en.wikipedia.org/wiki/Essential_oil

You can try crushing fresh vegetables and using the juices. Just make sure you document how many cloves (for example) for your Methods.

Anything that comes in a bottle should give you some sort of concentration.

I hope this helps. Let us know if you need more clarification.

Best,
Heather

Thanks for the answers!
I just talked to my teacher today, and there are two problems.
1, She does not have any E. Coli
and 2, She wants me to somehow get the E. Coli (or a usable bacteria) from the ground, and buying it from Carolina or whatever won't cut it.
SO, how do I get E. Coli (or anything else) from the ground?!?
Help!
Audrey

Hi Audrey,

It is a bit unusual for your teacher to request that you collect your bacteria from the ground, because you will not be able to tell exactly what species you culture from the environment. Also, there is a potential for you to culture harmful strains of bacteria, whereas ordering E. coli from a company ensures that you get a benign lab strain. That said, you can culture bacteria from the environment for your experiment.

Please read the "Projects Involving Unknown Microorganisms" section of the Microorganisms Safety Guide (https://www.sciencebuddies.org/science- ... fety.shtml) to see what I mean. You could try arguing that ordering a lab strain of E. coli is safer, but if that does not convince your teacher you can plate bacteria from pretty much anywhere in the environment. In the case of collecting bacteria from the environment, you will probably not know what species you have (and you will likely have several types).

I hope that helps.

Heather

Well, I have managed to persuade my teacher that this is a bad idea. However, she says that the bacteria would take a week to ship.
Is there a way to get the bacteria faster? If anyone knows a place that ships faster, let me know.
Audrey
PS is there another strain of bacteria that I could use?

Hi Audrey,

Carolina Biological Supply (www.carolina.com) has several shipping options, including 2-day and overnight shipping. The faster options cost a bit more, but that will expedite the process. You'll want to order the MM294 Slant Culture (Item # 211530), and your teacher will have to do the ordering. Carolina only ships to schools, not to individuals.

I hope that helps!

Heather

Hi Audrey,

This may be a little too late and you may have already gotten the E. coli, but one good thing to keep in mind is that if you don't want to order the E. coli, another thing you can try doing is to find a local university microbiology lab that works with E. coli and ask them if they can give you some bacteria. Most labs are pretty good with helping students out with science projects, and giving you some E. coli on a plate should not be too big of a deal. That way, you can get the bacteria for free and you don't have to worry about buying the bacteria from vendors, which can sometimes be a bit pricey. Just something to keep in mind in case you ever decide to do any future projects on bacteria!

Best,
Connie

Well then.
It's been a long time since I've posted, and some things have changed.
First of all, I will pick a colony of bacteria from the ground and then grow that strain to test it (no more E. Coli).
Secondly, I have another question
What should be my dilution of my essential oils? Most websites recommend a 2% dilution for topical use; I that what I should use as well for my project?
Thanks so much to all the people who responded, by the way.
Audrey
*edit: after doing my lab work in school, I have created a 1/15 dilution (or 2/30, which it actually is). that way, I can change it according to any advice I should receive

Hi Audrey,

I recommend you do a Google/PubMed search for essential oils and antibacterial properties to see what other people have done when testing similar subjects in terms of an appropriate dilution. One paper that I found did a series of two fold dilutions, which would give a range from 50% down to less than 1%. You may also want to test a range of dilutions. Otherwise, if a 2% dilution is generally considered appropriate for topical use, then that seems like an appropriate dilution to test antibacterial effects at. Just be aware, that it may be too dilute to see much, which is an interesting finding in and of itself, since it implies that these oils are not significantly antibacterial at commonly used concentrations.

Hope this helps!
JMP