Bacteria are tiny one-celled creatures. This one cell contains all of its life giving structures. Like us and all other living things, bacteria breathe, take in food, reproduce and get rid of wastes. Many of them can move around and, in time, all of them die.

Bacteria are very, very small, so small that millions of them can live inside this letter. They can only be seen through a microscope.

There are thousands of kinds of bacteria. Some of them cause disease, but most are either harmless or beneficial. Many of these good bacteria help bio-grade break down dead plants and animals. They recycle their nutrients and return them to the environment for living plants and animals to use.