Although you can't use harmful bacteria in the child care setting, you can show how they grow. You can also make children more aware of food safety issues. Here are some activities to try. Dissolve yeast in hot, warm, cold, salty, and sugary water to show how temperature, salt, and sugar affect the growth of bacteria. Cold temperatures and salt slow down bacterial growth.
Warm water encourages bacterial and yeast growth.
Adding small amounts of sugar to warm water provides food for the yeast so it grows even faster. But very hot water or a lot of sugar will stop the growth of bacteria. That's how jelly and jam are preserved. This can help you explain how we can spread germs to others. Contact your local high school science teacher or hospital about how to obtain agar plates.