Eww, Bacteria!

It never fails. Science can be really, super gross. It can be an eye-opener. And boy, is it oh… SO… fascinating.

Take our bacteria experiments for example. I love doing this with kids of all levels because the reactions are totally classic, especially when looking at the bacteria colonies under the microscope:

(Wait for it…)
“Whoa, that is SO COOL!!”

I get my bacteria kits from Home Science Tools, because they have everything I need to run the experiments (plus, their catalog is like a candy shop… It’s a science lover’s dream).

A few years ago I did the Hand Washing Bacteria Kit with a small group of second and third graders after having to remind them about 60 kajillion times to wash their hands before lunch.

That’s right, 60 kajillion… At least that’s what it felt like.

This time the Bacteria Experiment Kit was a must with the middle and high school students because they weren’t doing their classroom cleaning jobs.

So, I wanted to show them the funk they were allowing themselves to wallow in.

The result was a double-whammy of captivation and disgust.
HST’s Bacteria Experiment Kit instruction manual gives a few different examples of using the bacteria kit. Wedid our own version, only because I’m a rebel, but still used large chunks of the instructions since they are an excellent guide.

At our morning meeting the day of the tests, we reviewed what we had learned so far about bacteria, and of course – as most middle and high schoolers do – we heard lots of really disgusting stories about their own personal experiences.

Nice. Thanks for the visuals.

My favorite part is talking about the theories of how bacteria came to be on Earth, which really got some awesome sci-fi stories going.

Then we got to business. I broke them up into groups:

  • Group 1: Bacteria in the Air (setting out the media to collect floating bacteria)
  • Group 2: Objects around the classroom (definitely the bathroom, among other places)
  • Group 3: Unwashed Hands (this speaks for itself)

(Note: I highly suggest getting more sterile cotton swabs. Consider doing “touch plates” for the unwashed hands, where you dab the fingertips and other parts of the hand onto the media instead of swabbing. This will give your more swabs for other dishes.)

Here is our process and results in photos. At the end of the post, I’ve given a list of other great resources I use to supplement this fun and inexpensive experiment.

Melt the agar until it’s liquid. Using the hot bath route, make sure the water is boiling hot.
These are our “air bacteria” plates. Label them on the bottom of the dish.
The bottle is super hot. Pour just enough to cover the bottom.
Gently roll it around to cover the bottom of the dish. Immediately cover with the lid.
Let the media/agar solidify, then let the kids place them in their proper areas to collect the air (take the lids off).

Waiting for funky bathroom air to settle onto the media… it doesn’t take long. Just let it sit for about an hour.

Grab a sterile swab (leave each one in the package until it’s ready to be used so it doesn’t get contaminated)

Swabbing the natural log in the fire belly toad tank.
VERY gently “streaking” the swab tip under “F” for frog. The “S” is for the gecko’s tank. The solidified bubble texture eventually went away… word to the wise, do not vigorously shake the agar bottle before pouring!
The bathroom faucet handle.
Streaking the plate with the cotton swab is like a zig zag.
The toilet seat. Ew. Better him than me.
The streak. Then it was the floor right around the toilet. Gross.

Phones, hands, Izzy’s mouth.. you name it, we swabbed it. Or at least considered it. Then, we loaded the covered plates on a tray – including the “air” plates we collected after an hour – placed the dishes in a closet, and let them sit for a week.

One week later, we got to use our colony  morphology skills to decipher the types of bacteria our tiny school likes to grow:

Frog and gecko’s tanks.
Playground air
Bathroom air
Bathroom faucet handle
Kids playroom air (two kids, age 3)
Main room air
My table and the main room table
A student’s phone – not so bad. But this brought up the discussion of what time of day we could try swabbing it next time. He also revealed to us that he had cleaned his phone the night before.
A hand of a student.

These were only a few of the bacteria dishes we uncovered. Their reactions were priceless, and some were so grossed out they refused to get a closer look under the microscope!

Seeing it under the microscope (also from Home Science Tools) gave us a more up-close observation of the different colonies that were growing. We were able to decipher most of the bacteria using the images in my Kingdoms of Life Connected manual.

Remember that any age level can do this experiment. It’s often a huge eye-opener for the grownups too!


To supplement the bacteria kit for all age ranges I like to use:

About Miranda

* Pisces. Eclectic. Indigo. Mother. Wife. Teacher. Herbalist. Scientist. Fantasy. Outdoors. Ocean. Crafty. Dreamer. * Found out more in the About section.

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