What are bacteria?

  • Bacteria are among the smallest living things.

  • A single bacterium consists of just one cell.

  • Not all bacteria are harmful to our bodies.

Chef Gennaro describes how knowledge of bacteria helps with food hygiene in his kitchen

What are bacteria?

Bacteria are among the smallest living things. A single bacterium consists of just one cell, and is called a single-celled, or unicellular organism.

Even though it is just a single cell, it can carry out all seven life processes (movement, respiration, sensitivity, growth, reproduction, excretion and nutrition).

What’s in a bacterium?

There are similarities between plant and animal cells and a bacterium. They all share a cell membrane and cytoplasm. Bacterium also have a cell wall around them, like plant cells. However unlike most plant and animal cells, it has no nucleus. Instead, it has a circular strand of DNA, called a plasmid, that floats in the cytoplasm.

There are millions of different types of bacteria. Different types of bacteria have different shapes.

Many types of bacteria have extra cell structures to help them to survive. For example, they may have:

  • Flagella, which are tail-like structures that allow bacteria to move through liquids.

  • A slime capsule, outside the cell wall, to protect them and stop the bacterium drying out.

Why is it useful to know about bacteria?

Some bacteria cause diseases, including food poisoning, meningitis and scarlet fever. Inside the body, these bacteria reproduce quickly. They produce poisons that make you feel ill.

Among the people that need to know about bacteria are chefs. Anyone who cooks needs to know how to prevent bacteria spreading in their kitchens, to ensure all the food they produce is safe to eat.

Not all bacteria are harmful. For example, yoghurt and cheese makers use bacteria to make their products. Bacteria like intestinal flora can be helpful to our bodies whereas E.coli can be harmful and cause disease.

More importantly, there are millions of bacteria in your digestive system. Having the right mix of bacteria here is vital. Gut bacteria help to digest food. They also help to prevent diabetes, obesity and some types of cancer.

Bacteria quiz

Test your knowledge of bacteria with this quick quiz.

Where next?

Discover more about this topic from around Bitesize.

What are cells?
How to make a model animal cell
How to make a model plant cell