Science Buddies: "Ask an Expert"

My project this year works with tannins (tannic acid) which is found naturally in bark, cranberries, and other organic material that has been found to possess antimicrobial effects. First found in cranberry juices to inhibit e.coli, tannins are being explored as an alternative medicine to antibiotic resistant bacteria. They have been found from the perspective of an atomic force microscope to react with the e.coli at a molecular level, inhibiting its infectious ability by changing the structure of its membrane.


An additional part of my project involves a recent study that the addition of sugar improves the effectiveness of an antibiotic to supposedly antibiotic resistant bacteria. Together, I would ultimately like to test a tannic acid concentration mixed with sugar on tannins-resistant e. coli to see if the same that holds true for antibiotics can be applied to naturally occurring antimicrobial compounds.


My main question is that would it be possible to acquire tannins-resistant e.coli or make a live strain of e.coli resistant to tannins with continued exposure? My only problem with the latter is that it is unknown how long that would take. The only resistant bacteria that I have been able to find online is a kit to make ampicillin-resistant e.coli (which involves adding the gene plasmid U38 to the live e.coli strain.)

From the research that I have all ready done, tannins-resistant bacteria have been found in the rumens of goats that eat tannins-rich food, if that offers any assistance.
Thank you very much.

Hi Dahliu,

Welcome to Science Buddies! This is a great idea for a science project. You have obviously been doing your background reading on your topic and you have a very specific, unique problem identified to investigate.

It would probably be easier to isolate bacteria that are already tannin-resistant by culturing them from sources that are naturally rich in tannin. Goat rumen samples would be good, but might contain pathogenic bacteria. Tree bark would probably be a safer sample source. The kit that you found on-line would work if you decide to develop your own strain, but that might take all of the time you have for this year. However, this topic could easily be a two-year/two-project endeavor and you would be able to do it since you are in 10th grade now.

Since you are thinking about culturing bacteria, you should check with your teacher and review the rules for projects involving potentially hazardous biological agents. You probably need to have access to a microbiology laboratory and someone with microbiology experience to provide advice. Here is information from the Science Buddies website.

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

Let us know if you need more information.


Donna Hardy

Thank you very much! Should I contact some microbiology labs to help me with this project?
Also, could I just expose the bacteria to ascending concentrations (starting from low to high) of tannic acid?

I was wondering when culturing this bacteria to be resistant, should I simply just use the same plate over and over again?
Here is the current method (roughly) that I am planning to do this. I hope to get this done before January 20th.

Rough:
Part One:
The objective of part one is to expose the e.coli to five different exposure solutions of the tannic acid to develop resistant strains.

1. Prepare the sterile filter disks. Hole punch the filter paper to make small discs and wrap them in aluminum foil and sterilize in a 300 degree oven for 30 minutes.

2. This is preparing the first disk/ exposure. Mark the uniformly distributed places where you shall put the disk.


3. Just remember the disk is for low exposure, and then use the proper sterile technique to inoculate each plate uniformly. 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. Cover the plate and wait at least five minutes for the plate to dry.

4. Now use forceps time. Use these forceps to take a single disk. Dip it in the 1st exposure solution. Place each of these disks in the center of each of the marked sections on the plate. Use the forceps to gently press each disk against the agar surface to insure good contact. Remember to use the exact same technique for each disk—consistency is very important for this experiment.

5. Incubate the plate overnight or longer if necessary.