do try this at home! — a Discovery Project perfect for corona-times!

I thought I’d try something new today and post a Discovery Project.
Feel free to:
a) immediately disregard this if you already have so much on your plate that the mere whisper of a word like “project” sends cold chills racing up and down your spine.
b) give it a whirl whether or not you have school-age children at home. I, personally, am going to try this!
c) bookmark this for some other time.
d) share it with someone who might enjoy it.

This is a science project and it fits our moment perfectly given the dramatic rise in our awareness of germs in our midst.

I’ll give you all the directions,
followed by a Q&A with my son, a microbiologist.
I’ve also got a few book titles that would pair swimmingly with this exercise, for those of you with access to such things, and a few web links for those of you who want to follow up that way.

Microbiome FINAL-01_0

The title I’ve given this project is:
Mystery Microbes
However! Harry Potter nerds can feel free to call it Microbia Aparecium!
10 points to Gryffindor if you can figure out why.
I’ve put one extra-special twist in the directions for you Hogwarts students to follow.

Project Aim:
Make your own, homemade “agar” Petri dishes and use them to grow colonies of microorganisms you can observe.

from Steve Spangler Science

Microbes are everywhere, but they are so tiny they can’t be seen with the naked eye. Culturing microbes –feeding them what they love and letting them grow rapidly in a controlled space — lets us see large groups of these fungi and bacteria. It’s fascinating to get a glimpse of the mighty, mysterious, secretive, organisms in our houses, in the air, on our skin, everywhere!

Screen Shot 2020-04-03 at 10.55.15 AM

1 beef bouillon cube or 1 tsp bouillon granules
1 cup water
1 teaspoon sugar
1 packet unflavored gelatin — find this with the Jello in your grocery store — OR 1 Tablespoon of agar-agar, which can be found in Asian specialty stores
a saucepan
containers: petri dishes if you happen to have them OR substitute foil muffin liners, clear plastic cups, small yogurt cups, small, flat deli tubs, clean baby food jars, or deep jar lids like the lid from a peanut butter or mayo jar;  you want the containers shallow, so you could even cut some yogurt cups down to about 1-1/2 inches high. Sterilize any previously-used containers thoroughly. Keep all containers covered once they are clean, to avoid contamination.
plastic wrap if needed to act as a lid; lids need to be clear
cotton swabs
something to label your containers, like masking tape and a black marker

Step One:
Read all the directions to familiarize yourself with the project, and gather your supplies.

Step Two:
Make the microbe food, also known as media.

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In the lab, scientists use agar media, a special substance that provides just the nutrients and conditions these little buggers need to grow. We are making our own home brew.

1. In the saucepan, combine bouillon, water, sugar and gelatin or agar-agar. [Note: I wondered whether a person could use 1 cup of beef broth in place of the bouillon+water.  I don’t have an answer on that. My hunch is that yes, you could if you cannot find the cubes/granules in your store. Worth a try.]
2. Bring it to a boil, stirring to dissolve the ingredients. This should take about a minute on a slow boil.
3. Turn off heat and cover the pot. There is bacteria in the air and you don’t want to contaminate your mixture.
4. Let it cool for about 10 minutes. That is less time than it will take for the gelatin to start setting, but enough to allow it to cool slightly for safer pouring and to prevent melting the plastic containers you are using.
5. Pour the mixture into your clean containers. Wait to remove the lids until you are ready to pour — we are trying to keep them as free of contamination as possible. You want them about 1/3 to 1/2 full.
6. Cover the containers loosely with their lids or the plastic wrap, and allow the mixture to cool for awhile on the counter. This step is intended to minimize the amount of condensation building up on the lid.  Then tighten the lids and let them cool completely in the fridge. It should set up like Jell-o in about 4 hours. (If using muffin liners, you could put them in a muffin pan for the pouring and cooling, and once they are set you could remove them from the pan and pop the whole thing into a ziplock bag for easier storage.)
7. Store them in the refrigerator until you are ready to use them, but don’t let them sit for more than 2-3 days before finishing the project.
8. Do not touch the agar! You will contaminate it.


Step Three:
Decide on what surfaces to test, or what tests to run.
There are lots of possibilities here.
1. You could choose several surfaces in your home — doorknobs, piano keys, faucet handles, TV remotes, computer keyboards, cell phones, toys, the dog’s dish, a toothbrush, etc.  In this case you will use cotton swabs, a separate one for each location. You will rub the clean cotton swab on the surface to collect microbes.
2. You could collect microbes from your own body — your hands, other family members’ hands, inside your mouth, just inside the edge of your nostril, your belly button, your hair. In this case you might gently run your finger across the agar surface, or swab the inside of your mouth, nose, belly button, or touch the agar surface with strands of hair, or even cough onto the surface.
3. You could collect microbes from outdoors. You could expose one dish to the air inside your house, and another to the air at a location outdoors, leaving the agar mixture exposed for about 1/2 hour in this instance. You could swab things like a leaf, the car door handle, your bike handlebars, the arm rests of a car seat, the inside of the dog house.
4. You could try a before-and-after test. Run your finger across one plate of agar, then wash your hands with soap and water for 20 seconds, dry on a clean paper towel, and immediately run your finger across another plate. The more elaborate these before-and-after tests are, the more you will have to think ahead to eliminate as many variables as possible other than the one you are testing. For example, if I want to test whether washing for 20 seconds is really better than washing for 5 seconds, I would need to wash for 5 seconds, immediately test, and then continue washing without adding more soap or changing the water temperature. I would need to swipe with the same finger or use a swab to test the same section of my hand. In a non-laboratory setting, we will still get contaminants and variations, but try to think through and eliminate as many as possible.
5. You could test one plate by rubbing a large area with a dirty finger, then putting a small drop of sanitizer in the middle to see what happens.
6. If you want to test more samples than you have plates of agar, you can divide the plates as long as the containers are clear. Do this by drawing a line or grid on the bottom of the plate with an indelible marker so you can see it through the agar. You can divide it into two or four sections. Label each section with what you are testing. You are doing this on the bottom because if you did it on the lid, it could move and then you won’t have the label matched to the correct quadrant.
Note: Collecting things from a human source rather than non-human such as a leaf or a rock, will make a culture easier to grow because most bacteria don’t like growing on a plate, but human-sourced bacteria are more apt to thrive there.  However, if you swab something like a fallen log, be patient, let it culture longer, maybe a week or more, and you might end up seeing something interesting.
7. Label all of your agar plates or quadrants with the marker, according to the tests you want to run, before you begin your collection.


Caveat: Be smart and don’t test an area that could have dangerous germs. For example, one of my son’s undergrad students had the idea to swab the inside of an ambulance. Granted, there would be a lot of interesting microbes there! But there’s a high potential for hazardous microbes, of course. If you test in your home or back yard, you should not need to worry about what you are culturing.

Note: You do not need to worry that you are accidentally culturing the COVID-19 virus. See the explanation for this in my Q&A farther down the blog.

inoculating an agar plate

Step Four:
Collect microbes!
1. Swab the surfaces, then immediately remove the lid and gently rub the swab on the section labeled for that surface, using a zig zag pattern. If you do this gently, the agar won’t break. If it does break, you have not ruined your experiment; just carry on.
2. Immediately put the lid back on securely and set on a flat surface at room temperature or in a spot that stays extra warm — about 95-98 degrees but not hotter than that.
2b. Now, here is the special Hogwarts Twist! Grab your wand, wave in a zig zag pattern over your cultures and proclaim the spell: Microbia Aparecium! Did you figure out why this is the right spell for this project?


Step Five:

Depending on the temperature of your room, it might take 3-5 days for the cultures to become large enough for you to observe. As you watch them grow, you can document your discoveries by:
~Taking photos at specified intervals.
~Drawing what you see from day to day, noticing sizes, colors, shapes of what grows.
Ask curious questions: What does it look like from on top? From the side? From the bottom? What does the surface look like — smooth? rough? wrinkly? shiny? dull? What does it look like under a magnifying glass? Do not use your other senses — smell, taste, touch — to make your observations! Keep the lids on.

appearance of colonies on agar plates

This chart shows the forms and terms used to describe cultures.

You will probably have cultured fungi (molds) and possibly some bacteria. My understanding is that bacteria tend to be more perfectly circular or globular, and fungi tend to have fuzzier edges.


Step Six:
Share your results.
I’d love to hear of your results.  Feel free to comment, to send me a photo of your cool colonies at, or to tag me on Instagram @orangemarmaladebooks

Step Seven:
Dispose of your specimens
After a couple of weeks, it’s time to get rid of these cultures. Do not re-use these containers. Simply leave the lids on and toss the whole business to avoid any possibility of harm to yourselves.

Step Eight:
Follow up with my Q&A and further resources.


Q&A with Erik-the Microbiologist!

Q: Hi, Erik. Are you in your lab today?
A: No. I can’t be there right now because of the COVID-19 restrictions.

Q: Oh, sorry. Well, my first question is: What is a microbe?
A: A microbe is an organism that’s so small, it takes a microscope to see it.
These are organisms like bacteria, viruses, fungi — yeast, for example.

Q: Is that the same thing as a germ? Or what exactly is a germ?
A: A germ is just an ordinary word people use when they mean a microbe that makes us sick.

Q: Are most microbes germs?
A: No. Most bacteria don’t make most people sick. There are trillions and trillions of microbes in the world, and most of them do not do us harm.

Q: What’s the difference between a bacteria and a virus?
A: A bacteria is a living thing that consists of only one cell and doesn’t have what we call organelles. Scientists call these organisms Prokaryotes (say: pro-carry-oats). Even though they are so simple, because they are living things they can replicate themselves, which means they can make copies of themselves and grow.  A virus is not technically a living thing, in the way biologists categorize things, because it has no way of replicating by itself.  In order for a virus to make a copy of itself, it has to hack into another cell and use its replication mechanism. Once it does that, it replicates itself until there are so many within that one cell that the cell ruptures. Then all those copies of the virus can find more cells to infiltrate.

Q: Is COVID-19 a bacteria or a virus?
A: It’s a virus.

Q: How can washing my hands with soap and water get rid of COVID-19 viruses?
A. There are two ways. First, it simply washes it off. Second, the soap molecules break the packaging of the virus, what we call the capsule, which is like a thin outer coating. Once that’s broken it can’t insert itself into a cell anymore.

Q: Why do antibacterial wipes get rid of viruses?
A: Most of them are alcohol wipes and alcohol breaks up cell membranes the same way it breaks up viral capsules.

Q: If I do this experiment, could I accidentally culture COVID-19 and cause a huge problem in my household?
A: No. Viruses don’t grow on plates and they can’t infect bacteria so it won’t have anything to infect on your plate.

Q: Why do scientists study microbes? Is it only to keep people from getting sick?
A: That is a huge question. 98-99% of all organisms on earth are microbes, so there are obviously a lot of areas to study. That ranges from medical concerns, which is a lot of what we study because we care about people’s health, to agriculture, climate change, pollution, even snow.

Q: What microbes are you studying?
A: I am mostly studying a genus of bacteria called Frankia.

Q: Do you like being a scientist?
A: I do! It’s a lot of work, but getting to explore my own ideas and figure things out is a lot of fun and very rewarding.

Q: If I want to be a scientist, what’s a good thing to learn about now?
A:  I’d say, learn how to figure things out on your own. In most jobs you learn how to do something from somebody else, but in science you are doing new things, things you don’t know how to do and no one has done before, so you have to learn how to figure things out, and that’s something you can practice.

Q: Thank you, Erik, for being our scientist-in-residence today!

If you want to follow up with some ideal books, here are some great choices:

For ages 3 and up:

tiny creatures cover image

Tiny Creatures: The World of Microbes, written by Nicola Davies, illustrated by Emily Sutton
published in 2014 by Candlewick Press

Microbes are so tiny, “a single drop of seawater can hold twenty million” of them. In fact, “there are more microbes living on your skin than there are people on Earth.” Time for a proper introduction, I’d say!

Acclaimed British author Nicola Davies makes this subject supremely accessible to young children and Emily Sutton provides gorgeous, inviting illustration work. Truly a brilliant piece of nonfiction.

For ages 7 and up:

all in a drop cover image

All in a Drop: How Antony van Leeuwenhoek Discovered an Invisible World, written by Lori Alexander, illustrated by Vivien Mildenberger
published in 2019 by Houghton Mifflin Harcourt
77 pages + back matter

This heavily-illustrated, short biography of the man who, in the 1600s, was the first to see microbes via his own, homemade, finely-constructed microscopes, is fascinating. Leeuwenhoek’s life inspires curiosity and persistence, and his discoveries evoke wonder and amazement as they revolutionize our understanding of the natural world. Read it aloud to curious kids ages 7 and up, or hand it to ages 10 and up.

For ages 10 and up:

the great trouble cover image

The Great Trouble: A Mystery of London, the Blue Death, and a Boy Called Eel, by Deborah Hopkinson
published in 2013 by Alfred A. Knopf
272 pages

This is a superb piece of historical fiction taking place in London, in 1854. Through the life of a 12-year-old orphan named Eel and his good friend, Florrie, we experience the cholera epidemic that swept their London neighborhood, and meet Dr. John Snow, the father of epidemiology. Snow’s conviction that cholera came not from the foul air, but from contaminated water, and his dogged determination to scientifically track and prove his theory, revolutionized public health.

With its Dickensian atmosphere, its mix of adventure, mystery, sorrow, kindness, and community, this is a gripping novel perfectly suited to the present moment. Hopkinson also provides extensive notes about the historical figures met in the book and the Broad Street cholera epidemic. An excellent choice for ages 10 to adult, also available as an audiobook.

For older teens and adults:

i contain multitudes cover

I Contain Multitudes: The Microbes Within Us and a Grander View of Life, by Ed Yong
published by HarperCollins in 2016
357 pages

I gave this book to my husband for Christmas a few years back and he devoured it.

Yong provides a magnificent and entertaining portrait of the amazing world of microbes within animal and human bodies. Meet the scientists who have and are discovering the grandeur of our microbiome, learn about the fascinating ways these systems are used by various creatures, the many powerfully good roles they play within our bodies and world, and some of the ways scientists are pondering putting microbes to work in the future.


A few web links for learning more about microbes:

A 4-minute TED-ED video called You Are Your Microbes, geared for about ages 8-12.

Kids Discover  magazine had an issue devoted to Microbes. You can sign up for a free account to access three of the articles — one about Leeuwenhoek, one about useful microbes, and one about microbes in extreme environments;  a premium account is needed for the rest. Beautifully put together. Geared for upper elementary through middle school.

A nice sequence of pages about everything microbial with gobs of information, though less graphically-appealing. For middle school and up.

Did you know scientists hold agar art contests? If you look up agar art you can find images like this one…

agar art contest

…which they create by carefully streaking the agar plates.


That’s it for today.
If you’re willing, I’d love to hear in the comments whether a project like this is helpful to you.