Grow microbes on bread

All around us are tiny living things too small to be seen with the naked eye. We call these microscopic organisms, or microbes. 

Microbes are everywhere. In fact, our bodies are home to many microbes that are essential for our health.  But not all of them are good. Some microbes can make us sick, which is why hand-washing is important. How well do you wash your hands? Let's find out.

In a science lab, we use a Petri dish to grow microbes. The dish contains a layer called the 'medium' which has all of the nutrients microbes need to eat and grow. But with a few simple household items we can create our own medium to watch microbes grow.

Materials

Sealable plastic sandwich bags

Clean tongs

Bread slices

Marker

Steps

1. Use clean tongs to place a fresh slice of bread in a sealable plastic sandwich bag. Take care not to touch the bread or inside of the bag with your hands – you don't want to add extra microbes! Seal the bag and mark it as “control”. The control in an experiment is used to make sure that any differences you see in the results are because of the things you are changing. In this case, we want to see changes that result from washing your hands, as opposed to microbes that may naturally be on the bread anyway.
2. Take another slice of bread using the tongs. This time, gently touch your hand on both sides of the slide (without washing your hands!) then place the bread in another plastic bag. Seal this bag and mark it as “unwashed hands”.
3. Now wash your hands with soap and water for 20 seconds, then repeat step two with clean hands. This time, mark the bag as “washed hands”.
4. Place the sealed bags in a cool, dry location.
5. Check on them once a day for a week to see if there are any differences on the amount of mould and bacteria growth on the slices of bread. Do not open the bags during the experiment.
6. Which slice or slices do you expect to see growth on? Washing your hands with soap and water removes dirt and microbes, and can also literally rip apart some viruses and bacteria – but that doesn’t mean that you can get rid of all of them. Plus, there could be microbes on the bread itself.

   

Bonus activity

Here are some ways you can extend this experiment:

Ask your friends and family members to do the experiment with you. Do different microbes grow on their bread compared to yours?

Try using hand sanitiser to clean your hands. How does the result compare to soap?