Wednesday, January 28, 2015

Culturing Bacteria in your Classroom

Do your students LOVE science? This activity is the perfect thing to teach students why we wash our hands and clean our desks! Plus, it is actually super easy to do. It does take some prep on your part before you start though. You will need a box of gelatin, water and sugar. The growing process takes about a week or so, but you can speed it up by adding a cube of beef bouillon. You will also need q-tips and small containers with lids (or plastic wrap).
{Please Note: I doubled the following recipe to have enough agar for all of my students to grow their own bacteria. You can have your students complete this in groups or individually.}

Agar Directions:
1. Bring 1/2 cup water to a boil.
2. Mix in 2 teaspoons of gelatin and 2 teaspoons of sugar.
3. Stir until it is well dissolved {add a cube of beef bouillon if you want your results sooner}.
4. Carefully pour a small amount of the agar into your containers. You will want your containers to have a lid. You can use small dixie cups and just cover with plastic wrap if you don't want to buy the little mini cups with lids.
5. Chill the containers overnight.

Lab Directions:
1. Label container with initials and test location.
2. Swab the test location with one end of the q-tip.
3. Open container and carefully swab {with the same end} on the agar.
4. Close container and place in a cool dark space.
5. Let the bacteria culture for 3-5 days.

You can make observations as the bacteria is growing. After about a week, you will see definite results. When we first start the lab, I always make sure that my students understand that not everyone's sample is going to look the same. That is my favorite part! All of the samples will grow different colored bacteria and mold at different speeds. Here are some examples of our containers before culturing.

The day before our lab, I sent out a quick e-mail to all of our staff to let them know what we would be doing. My students went anywhere in the school to take their sample. You can see in their labeled containers above, some of them went to their previous teachers, the lunchroom, the superintendent's office and one even swabbed their mouth. I told my students no one could swab the same place as someone else. Other places my students swabbed: keyboard, younger sibling's desk, nurse's office counter, principal's desk, and a toilet. The whole school was up for "swabs"! Then, we placed the samples in my back closet for 2 days before making our first observations. Only a few of my students saw results. A few days later, all of my students had some results!! Here are some after photos.
 As you can see, they are all different. If you look closely you can see little yellow dots on 3 of the samples. This is bacteria. You can also see three different variations of mold! So Cool!

It is so important for students to realize that mold/bacteria could grow anywhere however it needs the right environment to grow. That is why we put it in a cool, dark space. The agar that you poured in the bottom of the containers acts as the nutrition source for the bacteria.

Lastly, my students typed up their Lab Reports! They had to handwrite their drafts and then type them up on the iPads using the Pages app.
My students loved culturing bacteria. They couldn't wait to tell their parents all about it and bring home their lab reports {no... I didn't let them take home their bacteria}. I also e-mailed the few teachers/staff members where my students took samples from at the end of our project. All of the them let my students come into their classroom to read their lab report to their class! It was a great opportunity for all of my students to step out of their comfort zone and read in front of a group. It was low stress because they used their reports and they were "pros" on their own bacteria!

Just so you know, I created this product {STEM Challenge: Culturing Bacteria} to help guide my students through the lab. You could totally do it without though!! Let me know if you try out the lab with your students! I would love to see your results!


  1. What a fun idea! Thanks for including the recipe too.

  2. I was looking for a recipe for homemade agar! THANKS! This is a terrific lesson. I think I'd like to add this to my investigations this year.



We LOVE to read your comments, and prefer to reply by email so that you will receive our responses. Make sure you're not a "No Reply Blogger" or leave your email address in your comment.Thanks for stopping by! :)