How I Learned to Make Better Agar Plates

I started working with genetic engineering in January for my Grade 7 Science Fair project, and after competing in the York Regional Science and Technology Fair, I found myself wanting to continue in the field for future Science Fairs and possibly as part of a future profession.

This summer I received the DNA Playground as a gift from my parents. Since then I’ve been using it to improve my skills in genetic engineering. Amino Labs suggested I write a blog on their site about how I learned to make better agar plates, and I’m also going to try writing occasional learning blog articles on Medium as I improve.

I’ve done Amino Lab’s Engineer-It Kit 3 times now, and I’ve noticed a big increase in the quality of my agar and colonies, especially between the 2nd and 3rd try.

With the first 2 Engineer-It Kits, I felt that my plates were ok, but they seemed a little grainy at close examination, the second set of plates being slightly clearer then the first one. When heating, my agar didn’t reach the molten state.

The third time I tried making the plates they were very clear. That time I had put the sterile water in the microwave longer and warmed it up much more, and after putting in the agar, I kept it hot. After pouring the non-selective plate, I put the bottle in the microwave once more to make sure it hadn’t cooled off, then added the antibiotic. After pouring the rest of the plates and letting them dry, they were very clear. With the first 2 plate batches after I did streaking and let them incubate (before transformation), the E. coli was sort of opaque and “misty” and was even partly in the agar. It was like one flat lawn, without any ‘3d’ bumps of colonies, while the 3rd batch was normal with lots of colonies.

My third time with the Engineer-It Kit: the agar is very clear. The plate is about 10 inches above the petri dish bag label and you can still read it clearly. After streaking and incubation; the bacteria isn’t misty like in try 1 and 2. You can see colonies.

Each time I did the procedure, I felt that I knew more about what I was doing and more confident, especially after the 3rd time. The first time I did the Engineer-It Kit, I only got one colony. Then I got 6 the second time and a whole plate full the third time. I found the increase of colonies encouraging and it showed that I was getting better and more used to the procedure.

From left to right: the results from my first, second and third attempts with the Engineer-it Kit.

If you’re also learning the basics, I suggest that you heat your molten agar much more then you would expect is needed, heat the agar right before you add the antibiotic so it’s as hot as possible to help it melt, and to keep practicing your streaking technique — hold the loop near the end like a paintbrush to have maximum control!