Hello everyone! Last week I briefly mentioned an activity that I had in mind for part of my maker challenge lesson plan. I promised that I would go more in depth the next week , so I have dedicated this post to explaining my natural selection of viruses activity. I have included the background and outline of the activity so that you can have an overview before looking at the activity itself.

Background

Imagine jumping into the perfect pool on a hot summer’s day. The water is cool, crisp and clear thanks to a filter that helps to keep it clean. Now, imagine jumping into the worst pool. It’s probably green, grimey, and gross. That grimey gunk that lines the sides of the pool is known as a biofilm. Biofilms are layers of bacteria or algae that grow on surfaces, and they form in lots of places: pools, shower tiles, and even your teeth! Biofilms also tend to form on water filters, so if you don’t replace the filters regularly, bacteria can leak into your pool or even the water you drink! But, what if we could remove this biofilm without needing to replace the filter or releasing toxic chemicals into the water? Scientists have found a seemingly unlikely hero in viruses. Just like there are viruses that infect us and make us sick, there are some viruses that specifically infect bacteria. These viruses have specific structures on their surface that help them attach to the bacteria. Some even have special abilities to kill bacteria even faster using special enzymes. The problem is that there is more than one type of bacteria in these biofilms, and viruses are usually very specific to one type of bacteria. Scientists need a way to engineer viruses so that they can infect and kill as many different bacteria as possible. That’s when you come in!

In this activity, students will experience how some scientists are using the principles of natural selection to engineer viruses that infect multiple bacterial hosts. By sequentially changing the environment through switching out the type of bacteria, over the course of a few generations, scientists are left with viruses that can infect all of the different bacterial hosts. This model will help students visualize natural selection as well as the process of viral infection.

Materials

• At least 4 styrofoam balls/blocks (“viruses”)
• At least 20 sets of velcro circles (“surface proteins” and “bacteria”)
• Double Sided (or single sided, folded) tape (“surface proteins”)
• At least 10 small fuzzy pom poms (“bacteria”)
• At least 10 small squares of paper (“bacteria”)
• 1 container

Setup

First, you will need to attach the surface proteins to the viruses as outlined below:

• Virus A: soft velcro surface proteins
• Virus B: spikey velcro surface proteins
• Virus C: soft & spikey velcro surface proteins
• Virus D: double sided tape surface proteins (or single sided, folded as pictured)
• Virus E: soft velcro, spikey velcro, and tape proteins

For this demonstration you will be walking your students through the process of introducing your viruses to different bacterial environments. An outline of these different environments and the expected outcomes is shown below:

 

Challenges/Future Directions

• The tape was actually somewhat sticking to the fuzzy pom pom bacteria. Perhaps a different type of surface protein or bacteria will need to be used? Any advice is appreciated.
• It could be interesting to ask students which method they think would work better, sequentially exposing them to the bacteria or exposing them to all of the different bacteria at the same time (Figure 7).
• Merits/detriments of actually showing the viruses reproducing. Should they add one more of each of the viruses that attached? This could take extra time to prepare and explain but it could also be more accurate in showing natural selection.

 

Thank you for taking the time to read my lesson idea! Any and all comments/advice is much appreciated!