Science Buddies: "Ask an Expert"

Hello,
I am very interested in the lately very popular topic in microbiology about microbiota in our gut and effects of it on our mental processes. I've heard that the microorganisms in our gut regulate the secretion of neurotransmitters from the cells in the lining of our gut and I want to make an experiment that would investigate how nutrition affects it. Nevertheless, I am struggling with designing an experiment I would be able to carry out on my own.
I know I can research how nutrition affects growth of certain bacteria but I don't know which to pick. I've heard that E.coli could be used. However, how is this justified? Is E.coli the most frequent in our gut? If not, which one is the most representative?
The best possible scenario would be if I could detect the release of certain neurotransmitters, since that is what interests me the most. So, I was wondering whether bacteria in the gut secrete neurotransmitters on their own, besides promoting the secretion in human cells? Also, is there even an indicator I could realistically use to detect serotonin or some other neurotransmitter? If so, which one?
I plan on breeding bacteria in agar, containing different food sources. One would probably include glucose solution, but what should I put in agar in order to simulate the consumption of fat or protein? Would fatty acids for fats and a mixture of amino acids for proteins do?

Thank you for all your answers, kind regards,
Zala

Hi Zala and welcome to Scibuddies. Studying the microbes of the gut and how they affect human physiology is indeed a hot area of research right now and will certainly be continuing for a long time as the bacterial interactions are very complex.

The production of neurotransmitters (NTs) by gut bacteria and their affect on human mood was certainly a surprise to most scientists and we still don't know how it works. Bacteria do synthesize molecules like dopamine and serotonin that can affect human brain function and psychological state, but it is unclear how or whether these bacterial neurotransmitters actually make it to the brain: https://www.smithsonianmag.com/science- ... 180971411/

Unfortunately, most of the experiments that would be interesting to do are beyond the reach of a high school lab and your current skills. E coli is found in the human gut, but i do not think it is the predominant species. There is one I have read about called Coprococcus that produces NTs similar to dopamine in the human gut: https://www.sciencemag.org/news/2019/02 ... depression

One problem with doing meaningful experiments on gut bacteria is that the gut is an anaerobic environment, meaning that there is no air inside it--specifically no oxygen. Coprococcus will not grow in the presence of oxygen so has to be grown in special anaerobic culture jars from which oxygen has been purged: https://en.wikipedia.org/wiki/Coprococcus_eutactus

E coli K12 is the usual stand-in for all bacteria in high school lab experiments because it is cheap to buy, harmless to humans and does not require handling in a biosafety level 2 facility. Coprococcus can also be handled under BSL 1 conditions but a live culture costs $310 from ATCC and must be handled anaerobically:
https://www.atcc.org/products/all/27759.aspx
This would add more to the cost and make it more difficult to do experiments. If you could find a university lab that is doing research with coprococcus or some other gut bacterium and get them to agree to take you on as a summer student then you would be able to do a good project on gut microbiota and NTs.

E coli can be grown in air, but I don't know whether it would produce NTs under those conditions. You will have to do some online research to find this out.

You asked about detecting NTs such as serotonin and dopamine, and yes this can be done but it requires special equipment and chemicals not found in high school labs. You could, however, detect the effects of NTs on an organism--the roundworm C elegans: http://www.wormbook.org/chapters/www_mo ... mines.html

C elegans are cheap to buy and relatively simple to grow and experiment with. There are many Youtube videos that explain all about this simple lab animal and show what you can do with it. The worms are tiny, harmless to humans, require no special containment or growth conditions and have a variety of physiological functions that you can measure--like growth, egg production, learning and longevity.

It is easy to think up experiments using bacteria and roundworms but the difficulty comes in the details of how you do them. You will need basic lab equipment and a moderate degree of skill which takes practice. If you can find a person willing to explain the techniques to you, show you how to do them and watch while you learn, that is the best situation. I can tell you how to do things and give you links to YT videos that show the procedure, but having a person there to answer your questions and show you exactly what to do is always best.

Post again after you have thought about what you want to do and I'll see if I can help your create an interesting, worthwhile project that is doable with the resources you have.

Best wishes,
Sybee

Thank you so much for your comprehensive answer! I will keep you updated if I manage to carry it out

OK, Zala. But please don't hesitate to ask any questions. Make sure that your ideas and assumptions are correct. It is easy to get things wrong--even experts make mistakes--and the consequences can be be pretty bad. Better to verify a method or decision than proceed in error.

Sybee