A Shocking Bacteria Science Experiment: Grow a Germ Farm

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I used to think that my house was clean. It certainly appears clean and tidy.  There are no piles of trash or sticky countertops.  Who knew there was so much bacteria lurking? I’m so glad we did this bacteria science experiment!

We recently studied bacteria in our science program, NOEO Biology 2, by reading a bit of The Complete Book of the Microscope.  I love the Usborne science books because they include suggested experiments.  The book suggested taking a bacteria culture from hands, but we decided to take this bacteria science experiment a little further and culture other surfaces around our home as well to create our own little germ farm.

The results were quite shocking.

Bacteria Science Experiment

How to Grow Your Own Germ Farm

Growing bacteria cultures requires a few things:

  • Agar plates
  • Sterile cotton swabs
  • Bottled water
  • Tape
  • A heat source

I ordered this agar plate set because it included 10 agar plates and the sterile cotton swabs. I had everything else at home, so this was an easy bacteria science experiment to set up.

The procedure is fairly straight forward.

  1. Label the cover of the agar plates with the surface you intend to swab.
  2. Unwrap a sterile cotton swab and pour on a little bottled water.
  3. Swab the surface you want to test.
  4. Rub the cotton swab on the agar plate.
  5. Place the labelled lid on top and tape it shut.
  6. Turn the sealed agar plate upside down so that the name is on the bottom. This lets you observe the bacteria growth without the label being in the way.
  7. Repeat as many times as you would like, using a new agar plate and clean cotton swab with each surface.
  8. Place the bacteria cultures in a warm place.  Ideally, the temperature should be kept between 85 and 100 degrees.  We placed our tray of cultures in front of a space heater in the guest room.  The room stayed pretty toasty with the door shut.  I always turned the space heater off when we went to bed, for safety reasons, but the bacteria grew even with the cooler overnight temperature.
Check this out guide to growing your own germ farm. It is easy to culture bacteria samples.

We chose surfaces that we thought might harbor bacteria, even though they looked clean.

  • Dirty hands
  • Clean hands (we expected this to be bacteria-free)
  • Refrigerator handle
  • Door handle
  • Cell phone
  • TV Remote
  • Toilet Seat
  • Kitchen faucet
  • Trash can
  • Light switch

We looked at our germ farm each day, but let the bacteria science experiment grow for 3 full days before recording our results.

This bacteria science experiment will help you grow your very own germ farm. Follow these simple steps to culture various surfaces and try to grow bacteria. The results were shocking! This would be a great science fair experiment entry or a hands on biology lesson. #bacteria #scienceexperiment

Bacteria Science Experiment Results

After 3 full days we observed the different cultures.  I couldn’t find a way to determine exactly which bacterias, mold, and yeasts we were growing without a high powered microscope. We were able to use our microscope that connects to our tv to notice edge lines of the cultures, but nothing really detailed.  That’s okay though.  There was still plenty to observe.

We noticed the shape, size, and color of all the growth.  The colors ranged from a cloudy white to a creamy yellow.  There was even a few spots of fuzzy green.

What surprised us was the amount of microbes growing.  My house is generally clean!  Who knew we were surrounded by so much bacteria.

In order from least germs to the most –

  1. Light switch
  2. Door handle
  3. Toilet seat
  4. Cell phone
  5. Trash can
  6. Kitchen faucet
  7. Remote
  8. Clean hands (!)
  9. Fridge handle
  10. Dirty hands
This bacteria science experiment will help you grow your very own germ farm. Follow these simple steps to culture various surfaces and try to grow bacteria. The results were shocking! This would be a great science fair experiment entry or a hands on biology lesson. #bacteria #scienceexperiment

For the most part, the bacteria amounts were a little unsettling, but likely are not harmful.  There is no way for us to know if the bacteria grown is good bacteria or bad bacteria.  We are rarely sick so I’m not too worried.  Just a bit grossed out.  I have always heard that being too clean is worse for immune systems than living around a little dirt.  I guess that must be true.

We did take this as an opportunity to review proper hand washing technique again though.  A friend, who is a nurse, suggested singing “Happy Birthday” twice as a way to not skimp on hand washing time.

Hannah and Ben drew a few of the bacteria cultures in their science notebooks and wrote a few sentences about the experiment and what they learned.

Then we sealed the cultures up in a Ziploc bag and threw them away. They were beginning to smell a bit, which I took as a bad sign.  My husband joked that one day soon the bacteria would take over the house.

All in all, this was a fascinating experiment and one that we hope to recreate again soon.  I would love to test surfaces out in public.  Although, I’m a little afraid to see what is lurking on a Target shopping cart handle.

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  1. Hello! Appreciate your post! My 3rd grader is attempting this project for her science fair this weekend. We did the swabs Monday. And have kept then under a lamp for the last three days but nothing has happened …..did yours get condensation?! It’s the only thing I see. 🙁 Hope we didn’t botch her project.
    Thank you!

    1. Hi! We did have some condensation. The condensation formed under the lid and the bacteria grew on the agar plate. I wonder if maybe the lamp isn’t producing enough heat for the samples. Hopefully something starts to grow soon!

  2. I’m worried about leaving a heat source on all day when we’re at work. We’re going to attempt this for the science fair. Was thinking of an aquarium with maybe two green house lights to heat, but still worried about leaving that on. Any other suggestions or thoughts???

  3. We did this with dirty hands in the classroom. I took pictures of what grew and sent them to an expert. He first reminded me not to remove the lids under any circumstances. He then told me some of what was on there. The children in my class had nasty hands. There was staphylococcus, Ecoli, and psudamonis, Just to name a couple.

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