Every now and then I write a blog post about lab activities that worked in my nonmajors biology class. For example, I have written about reptilobirds (an activity combining meiosis and inheritance), staining banana cells to illustrate digestion in plants, and building models of protein synthesis with candy.
Here’s another topic that nonmajors (and everyone else) ought to know about: the development of antibiotic resistance in bacteria. If you teach biology, you might have learned about antibiotic resistance so long ago that you assume everyone else knows about it too. However, I learned this semester that the misuse of antibiotics is still a real problem. During the week before our “Bacteria and Disease” lab, one of my students came into my office with clogged sinuses. He looked miserable and said that he’d been sick for weeks. He then reported that he had taken some of his roommate’s leftover antibiotics, and although he felt better for a while, he soon got worse again. You did what?! Of course you got sick again! How could you not know that was a bad idea?! I scolded him (more gently than that) and mentally reminded myself that education really does matter.
Of course, our lab manual already has an activity that addresses antibiotic resistance. I tried it once or twice. Students used different types of colored pencils (representing various strains of bacteria) to fill in a diagram of lungs in the lab manual. When they tried to erase the pencil marks (i.e., used antibiotics to kill the bacteria), they discovered that not all of the marks would disappear. They were supposed to conclude that antibiotics don’t kill all types of bacteria. The activity was so dull, predictable, and ineffective that I soon abandoned it. For many semesters we’ve showed a video about antibiotic-resistant tuberculosis bacteria instead.
But then I read this article by in The American Biology Teacher and I decided to give one of the activities a try. It was appealing because it connects antibiotic resistance directly with something that nearly all students have done: taken a prescription of antibiotics. The simulation uses dice and inexpensive pony beads to model the evolution of bacteria over a course of antibiotics. The pony beads are in three colors to simulate three degrees of resistance to the drugs (we used green for least resistant, yellow for resistant, and red for most resistant).
After a brief introduction, each pair of students is given a petri dish containing a “bank” of 20 green, 15 yellow, and 15 red pony beads. Each student transfers 13 green beads, 6 yellow beads, and 1 red bead to a separate dish, which represents the body and the bacteria currently infecting it. Students are told they are taking antibiotics to fight the infection. They are then instructed to roll the die and record the number in a table. Rolling a 1, 3, 5, or 6 means they remembered to take the antibiotics and get to remove 5 bacteria from the body. Least resistant bacteria die most easily, so green ones are removed first. Once there are no more green ones, yellow ones can be removed. Red ones die last. Rolling a 2 or 4 means they forgot to take their drugs.
Critically, the next step is reproduction: Students add one more of each color bead that has survived in the “body.” This was the only stage at which students tended to make mistakes. Some pairs forgot to do the reproduction part entirely; others put green beads back in the body even after all the least resistant bacteria were supposed to be dead. Both errors change the outcome of the activity, so clear instructions are essential.
Students then repeat the roll/removal/reproduction steps. At each round, they record the number of bacteria remaining until no bacteria remain in the dish. Afterwards, they answer questions on the worksheet. Most of the questions are fairly straightforward, but we were surprised at how many students had a hard time articulating the relationship between bead colors (representing genetic diversity) and the events of natural selection (less “fit” bacteria were eliminated first, leaving the best-adapted to pass their resistance alleles to the next generation).
One of the strengths of this activity is that the bacteria fall into a spectrum of resistance. I’ve observed that even thoughtful students have trouble understanding why antibiotic-resistant bacteria would ever die in the presence of antibiotics. The somewhat-resistant yellow beads and the more-resistant red beads remind students that most bacteria are vulnerable to antibiotics, but some are more resistant than others. Natural selection acts on this genetic diversity.
Note that this simulation lends itself well to graphing activities. One simple idea would be to have students graph the number of bacteria of each color over time. Another would be to collect the data from the entire class and have students graph the relationship between the number of times the antibiotics were forgotten and the number of rounds of antibiotics required to kill all the bacteria.
The writeup in The American Biology Teacher is very good, with one exception: It is difficult to discern from the narrative that 5 bacteria should be removed at each round. We developed a handout that clarifies the instructions and includes a detailed table for recording data. If you want a copy, please leave a note in the comments section and I’ll email it to you.
Reference:
Spreading Disease – It’s Contagious! Using a Model & Simulations to Understand How Antibiotics Work. Eva M. Ogens, Richard Langheim. The American Biology Teacher, Vol. 78 No. 7, September 2016; (pp. 568-574) DOI: 10.1525/abt.2016.78.7.568
Awesome! I have a lab activity similar to this that simulates cancer growth and my students really enjoy it. I would love a copy of this! Thank you for sharing!!!
Certainly! I will send it to you shortly.
This sounds wonde cil! I would love a copy.
Absolutely. Check your email for the materials.
I’ve seen a similar lab using jellybeans but would love to see yours. Thank you!
I’m happy to share it. I will send it to you soon.
Hi. I’m biology teacher. I don’t know if this site is still active, but I would very much like the handout if you still email does…
We’re not as active in creating content as we once were, but we are still happy to share. I’ll send it to you shortly.
Hi, would you please send me a copy as well, thanks.
Certainly! I just sent it to you.
I’d love a copy, please
Sure! I just sent it to you.
Could I request a copy, please?
Absolutely; I just sent them to you by email.
Hi , can I please get a copy, this is great.
Yep, I emailed you!
I would love a copy of the instructions please.
No problem. I’ll send it to you!
Hey! Just got transferred to Biology from Environmental Science. Looking to grow my activities for Biology content and this looks great! Please email me a copy of the instructions!
Hi! I emailed you the activity. Thanks!
Hello, this activity looks awesome, can I please have a copy of this emailed too ?
Yep, I emailed it to you!
this sounds awesome–want to try it for my non-majors course! Would you please send me a copy? Much appreciated
Could you also send it to this email as well, in case the firewall catches it at Lee–our retrieval method is real pain–this is my home email. Thanks again!
Hey there, I emailed a copy to both your addresses. Hope it’s useful!
Hi! Could you email me a copy as well?
You bet! Sorry for the delay. I just sent you an email with the handout.
Thank you for the blog and the activity. It sounds like a great representation of bacterial resistance. Please send me the handout you created.
Hi! I just emailed it to you. I hope it’s useful!
Could I please get a copy of this?
Hi, it should be in your email. I hope it’s useful!
Hi, could I please get a copy of this!
Oh goodness, I’m sorry I didn’t notice your comment until just now. I just emailed you a copy of the activity.
Hello! I’d love a copy of this activity to use with my non-major’s biology class, if you don’t mind sharing. Thanks for sharing this great activity on your blog!
Thanks for your kind words! I just sent the activity your way.
I would love a copy of this, thank you!
Of course! We’ll send it your way
Would love a copy of this activity – it looks amazing! Thanks!
I’ll email it to you!
This is exactly what I was looking for as we wrap up a unit on antibiotic resistance. I would love a copy if you don’t mind.
Thanks
Chrissy (Bio teacher in NYC)
Thanks for your interest! I’ll send it to you in the next few minutes
I’m excited to try this with my non-majors. I would love a copy of this! Thank you for sharing your experience and insights!
I emailed you!
Hello from Spain, I’m very interested in this activity. I would apreciate if you could send me a copy on this interesting activity. Thanks in advance.
Maria
Hola! Por supuesto. I emailed it to you just now.
Hello! Love the activity. I’m currently on the hunt to find more interactive activities and simulations for my students. Could you email me this please? Thank you!
No problem. Sending it your way now!
Is there a copy of this to access? Thank you!
Would love a copy!
Sent! 🙂
I teach a HS microbiology course and this sounds great. I would love a copy, townsem@hpisd.org.
Hi! Sorry for the delay. I will email it to you shortly!
I would love a copy of this !
No prob. I’ll email you in a few minutes.
I would love a copy!
Sorry for the delay! I sent it your way.
Could you please email me a copy? This is great!
I emailed you just now!
I would love to see a copy of your lab writeup. Thank you!
I emailed you just now!