Bacteria

A living thing made of one cell

You're made of trillions of cells working together. A bacterium (that's one of them; lots of them are called bacteria) is a whole living thing made of just one cell. It eats, grows, and makes copies of itself all on its own!

Bacteria are so small you need a microscope to see them. They come in a few shapes:

• Rods, like tiny hot dogs
• Balls, sometimes stuck together in chains or bunches
• Spirals, like tiny corkscrews

No nucleus!

Bacteria are much simpler than your cells, and much smaller too. Here's what's inside:

• No nucleus! A bacterium's DNA just floats around inside the cell, in a tangled loop.
• A cell wall around the outside, a bit like a plant cell has.
• Many have a whip-like tail called a flagellum (fluh-JEL-um) that spins like a propeller so they can swim.
• Lots of tiny hairs that help them stick to things.

Good bacteria and bad bacteria

When people hear "bacteria," they often think of germs. Some bacteria can make you sick, like the ones that cause strep throat or food poisoning. But most bacteria are harmless, and lots are helpful!

• Bacteria in your tummy help break down food and even make some vitamins for you.
• Bacteria help turn milk into yogurt and cheese.
• In the soil, bacteria break down dead leaves into food for new plants.

Super-fast copiers

Bacteria make more of themselves by copying their DNA and splitting in two. Then each one splits again, and again.

When it's warm and there's lots of food, some bacteria can split every 20 minutes. In just a few hours, one bacterium can turn into millions!

That's why these tricks help keep bad bacteria away:

• Wash your hands with soap.
• Keep food cold in the fridge. Cold slows bacteria down.
• Cook food all the way through.
• If you get sick from bacteria, a doctor may give you antibiotics, medicine that stops bacteria. (It doesn't work on viruses, like the ones that cause colds!)

Bacteria quiz