Grow Germs Using Nutrient Agar

In this science experiment, kids use nutrient agar to grow germ specimens.

SAFETY NOTE:  ADULT SUPERVISION REQUIRED.  Germs can be dangerous and should not be touched or allowed to become airborne.  Once this experiment is started, it must remain sealed and be properly disposed of.  Preparing the agar also involves very hot water.

Germs, also called microbes, are so small that you need a microscope to see them. But rest assured – even if you can’t see them, they are everywhere! In fact, your body and most other things are covered with germs.  Most are bad for you, but some are good!

Bacteria and viruses are both examples of germs.

Bacteria are single-celled organisms that live just about everywhere on Earth – from boiling hot volcanoes to freezing cold icebergs. They can survive in environments where we humans cannot, and survive by eating everything from sugar to sunlight. Bacteria are very tiny; for example, 10 million can be found on your desk at school!  They can cause sicknesses like tonsillitis, strep throat and ear infections.

Most viruses are a thousand times smaller than bacteria. Unlike bacteria, viruses don’t have their own cell; they need to borrow a host cell, like a blood cell, to survive.  Viruses come in many funny shapes – some look like round popcorn balls while others have more complex shapes that look like spiders.  Viruses can spread quickly and cause sicknesses like chickenpox, the flu and the common cold.

Germs are a fact of life; they are everywhere, all the time. Though it’s important to avoid harmful germs by keeping your hands and body clean, there really is no way ever to get rid of the germs all around you.  That’s why your body has a highly effective system for dealing with germs – called your “immune system.” It acts like a superhero would, defending your body against invading germs.  For example, the tears in your eyes wash away and kill the germs that try to enter through your eyes; mucus traps germs and keeps them from entering your body through your nose; saliva kills the bacteria that try to enter through your mouth; the acids in your stomach kill the germs that manage to get past your saliva; and your white blood cells help attack and remove any harmful germs that start to float around your body.

It is important for us to study germs because they affect our bodies in many ways. Though many germs are harmful and cause us to get sick, scientists are learning that some germs are actually good for us!  For example, some germs in our mouths prevent other harmful germs from growing there; some are used in vaccines to keep us healthy; and some help us digest our food.

In fact, if you've ever eaten yogurt, you've eaten healthy bacteria! Two types of bacteria are used in making yogurt:  Lactobacillus Bulgaricus and Streptococcus Thermophilus. During the yogurt-making process, bacteria are added to milk; this causes a specific kind of fermentation to occur, which converts the milk into yogurt. These bacteria remain alive even after the yogurt is packaged and sent to the store.  A similar process is used to make other dairy products, such as sour cream.  Not only is this type of bacteria safe to eat, scientists believe these live bacteria may actually be good for your health by helping your digestive system, boosting your immune system and even fighting certain types of cancer.

Ever wonder how you can protect yourself from germs? Wash your hands!  Soap and water work best in the fight against germs.

Nutrient agar is made up of ingredients that will support the optimal growth of germs. It includes elements that the germs can both grow on and feed on.