Wondering what bacteria are? First, it helps to understand a bit about our bodies. Think of a brick house. All the bricks stick together to form the walls. Likewise, our body is built of building blocks. Instead of bricks, however, our bodies are built out of cells. These cells are extremely small. In fact, you can typically only see them with a microscope.
Bacteria are similar to the cells that make up our body. They are very small microorganisms, often much smaller than our cells. Bacteria are found almost everywhere on Earth. Right now, bacteria are probably living on your skin and in your body.
Many bacteria are helpful. They can help your body break down and digest food, for example. Some bacteria, however, like Salmonella, are harmful and can make people very sick. We’re going to take a longer look at bacteria, so if you have more questions or want to learn more, keep reading!
Bacteria are single-celled organisms. While our bodies are made out of trillions of cells, bacteria only have one cell. Like animals, many bacteria get food from their environment. Also, like animals, bacteria have a DNA blueprint, usually a “bacterial chromosome,” and can reproduce.
Quick Navigation
Bacteria Facts for Kids
- Bacteria are small one-celled microbes.
- Many bacteria eat food from the environment.
- Some bacteria create energy with photosynthesis.
- Many bacteria help our body in many ways.
- Some bacteria make us sick and are called germs.
- We know of more than 30,000 species of bacteria.
- Scientists often find new species.
What Are Bacteria?

Bacteria are very small, single-celled organisms (or unicell, as they’re sometimes called). Usually, to see bacteria, you need to use a microscope. Our body is made out of trillions of cells, while a bacterium has only one cell. Bacterium is used to describe one bacterial microbe, while bacteria is plural and used to refer to multiple bacteria.
Bacteria cells are different from our cells. A human cell will contain a nucleus that holds our genetic material or DNA. Cells with nuclei are called eukaryotic. Bacteria usually don’t have a nucleus and are called prokaryotes, which are the most common life form on Earth. Our cells also contain organelles, which are sort of like tiny organs inside our cells. Our cells have mitochondria, for example, that produce energy (kind of like our stomach). A Bacteria cell usually lacks these organelles.
Bacteria typically reproduce with binary fission. This means one cell divides into two cells. Often, these two new cells are identical to the parent cell (which no longer exists).
We know of at least 30,000 species of bacteria, and scientists often discover new species. Some bacteria are good for us. For example, bacteria living in your digestive tract right now may help you break down food. Many bacteria are harmless. Some bacteria are dangerous, and along with other bad microbes, like certain fungi, they are called “germs.”
Let’s take a longer look at some specific questions and topics regarding bacteria.
What are bacteria, and what do you do?

Bacteria are small, usually microscopic organisms. This means you typically can’t see bacteria without a microscope or another tool. Bacteria are living organisms. They must produce energy to live and often eat food that they find in the environment. However, some bacteria can use photosynthesis, like plants, to create energy. This means they use sunlight and other things to create energy.
Bacteria are found pretty much everywhere on Earth. Right now, bacteria are likely present on your skin. They may also be present on the computer screen, on your food, and in many other places. Most bacteria are harmless. Some bacteria are actually helpful. Many bacteria live in your digestive tract and help your body break down food. Some bacteria are harmful and may make you sick.
If you’re worried about harmful bacteria (and you should be!), there are things you can do to protect yourself. For example, when you wash your hands with soap, the soap will kill bacteria and other germs. Eating fresh, properly cooked food also reduces the risk of letting bad bacteria in when you eat.
What types of germs are there?
Germs are tiny microorganisms that can make people sick. Some bacteria are germs and can cause people to fall ill. If you’ve ever had a stomach ache (gut ache) it may have been caused by bad bacteria.
Not all germs are bacteria, however. Other microorganisms, including fungi and viruses, can also be called germs. What’s important to remember is that germs are bad microbes and can make people sick.
Further, not all bacteria are germs. Some bacteria are helpful. Many are harmless. These bacteria are not considered germs because they do not make you sick.
Why should I care about germs?
Probably no one likes being sick. When someone gets sick, they often feel bad. They may suffer an upset stomach, stuffy nose, or something else. Unfortunately, germs make people sick, and some folks may even end up in the hospital. Sadly, some people even die because they fall ill.
Germs can make people sick. By washing your hand, eating properly cooked food, and otherwise trying to avoid germs, you reduce the chances of becoming sick and getting a virus.
How can you protect yourself from germs?

There are many things you can do to protect yourself from germs. Washing your hands is one of the most important things you can do, but we’ll dig into that later.
Another thing you can do to protect yourself from germs is to eat healthy foods, including fruits and vegetables. Vitamin C and other nutrients found in fruits and vegetables may strengthen your immune system. Your body, and specifically your immune system, can fight off germs. Your body can produce cells and antibodies that can destroy germs.
Taking a long shower or bath and using soap will kill germs, including bacteria, on your skin. When you brush your teeth and use mouthwash, this kills germs in your mouth.
Cleaning, in general, can kill germs. If you wipe down your kitchen counter with soap, it will kill germs on the counter. If you touch a dirty counter with your hands, germs may stick to your hands. Then they can make their way into your body.
If you let food sit on a plate in your room for a few days, bacteria could grow on the plate. Then when you touch the plate, the germs could make their way into your body. Cleaning your room can reduce germs and thus help protect you.
Many germs get into our bodies by hitching a ride on food. Salmonella could be present in the chicken you have for dinner. If your chicken is cooked properly, the germs are usually destroyed. Proper cooking and using clean silverware, plates, pans, and more will help protect you from bacteria and other germs.
Why do you need to wash your hands?
We use our hands for many things. Let’s say you’re in the kitchen cooking, you pick up a piece of chicken or maybe some vegetables. Then you cut up the food and put it on a pan to cook in the oven. If germs were present on the food, they might now be on your hands.
Let’s say you forget to wash your hands and rub your eyes. Now, the germs may be on your eyes, and they can make their way into your body. Or perhaps you pick up another piece of food, say a cookie, and eat it. If germs were on your hands, they might have ended up on the cookie. Or when you put the cookie in your mouth, germs may have moved off of your hand and into your mouth.
If this happens, you may get an infection and feel sick. Sometimes the body catches bad foreign invaders, meaning germs, early. If this happens, you may not get sick, or you may only suffer a minor illness. If your body doesn’t catch the germs quickly, they can grow out of control and cause you to get very ill.
When you wash your hands, many of the germs are pushed off of your skin. When you use soap, the soap causes many viruses, bacteria, and other germs to break down. If the germs are destroyed before they enter your body, it could prevent you from getting sick. So by washing your hands, you may protect your health and avoid getting sick.
Why are germs so bad?
First, let’s remember that not all bacteria are bad. In fact, many bacteria live in our bodies and help with essential functions, like digestion. Some scientists refer to the entire collection of bacteria and other microbes as our microbiome. This includes both bad and good microbes. Among other things, good bacteria help our bodies break down carbohydrates and fatty acids, both of which are essential for us humans.
When we call a microbe a “germ,” however, it’s because the microbe is bad for us. One well-known germ is Salmonella, a bad bacterium sometimes found in food that can make people very sick. Doctors recommend that people avoid eating raw eggs and wash their hands after handling raw chicken. This is because Salmonella and other dangerous germs are sometimes found in chicken, eggs, and other foods. Salmonella doesn’t like heat, however. So when someone cooks food properly, the Salmonella usually dies.
What makes germs dangerous? Our bodies are extremely complex. When you eat food, your body and good microbes, including bacteria, break the food down into things we can use. Carbohydrates, for example, are used by our cells for energy. Your digestive tract is very long and consists of several organs, including your stomach, liver, intestines, and more. These different organs perform different things.
Throughout this entire process, different cells and microbes are doing different things. The same is true when you breathe, move muscles, or do anything else. Many processes are occurring, and your cells and microbes are hard at work.
Bad microbes, meaning germs, disrupt these processes and start to grow out of control. Bad microbes can overwhelm your body, causing many problems. Your lungs might fill with liquid, for example, making it hard to breathe. Salmonella, a bacterium, and germ, often infects the intestines and can grow rapidly out of control. This disrupts your digestive tract. Some bacteria also secret toxins into your body. As they grow, more toxins end up in your body.
Our immune systems are often very strong, and people with a healthy immune system can fight off many germs, including Salmonella. Sometimes your immune system is not strong enough. Medications, including antibiotics, can sometimes be used to help your immune system.
An antibiotic can help fight infectious disease.
When you get sick, however, your body and medications often hurt good bacteria too, which can also disrupt your digestive system and other functions.
