Scientists Say: Bacteria

Bacteria are one-celled creatures that live almost everywhere on the planet

Yellowstone National Park’s Grand Prismatic Spring (pictured) is a steaming pool of superhot, rainbow-colored water that gets its vibrant hues from the heat-loving bacteria that live there.

David Shvartsman/Getty Images

Bacteria (noun, “Bak-TEAR-ee-uh)

Bacteria are a type of microscopic organism, or microbe. Each one consists of a single cell. That cell has a simple structure. A bacterium does not contain a command center, or nucleus. Nor does it contain membrane-bound organelles. That makes bacterial cells prokaryotes. (More complex plant and animal cells are eukaryotes.)

Bacteria live almost everywhere on Earth. Some dwell on the seafloor. Others make their home in soil. Still other bacteria live inside our bodies. In fact, there are more bacterial cells in the human body than human cells. Some of these bacteria do useful jobs. Bacteria in our guts, for instance, help digest food. The bacteria and other microbes living inside a person’s body make up that person’s microbiome.

Most bacteria are not harmful. But some are pathogens that make people sick. Bacteria cause some mild illnesses, like strep throat. But they can also cause serious diseases, such as cholera and tetanus. Many bacterial infections can be treated with antibiotics. These medicines kill the bacteria or stop them from multiplying. Vaccines can also help protect against serious bacterial infections, such as tuberculosis.

Bacteria play countless roles in the environment and beyond as well. Some bacteria in soil break down dead plants and animals. This helps recycle nutrients so other organisms can use them. Bacteria at the bottom of the ocean gobble up the greenhouse gas methane before it can enter the atmosphere. Many industries also rely on bacteria. Food manufacturers, for instance, use bacteria to convert milk into products like cheese or yogurt. And some drugs are made using bacteria. One day, bacteria may even produce the fuel that powers cars.

In a sentence

The idea of “going with your gut” may be a lot more literal than you think — the bacteria that live inside our bellies can influence our mood, behavior and more.

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Maria Temming is the assistant editor at Science News for Students. She has bachelor's degrees in physics and English, and a master's in science writing.

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