Germs are bacteria, amoeba, protozoa and other tiny (microscopic) animals that may cause sickness. Most germs have only one cell, but they multiply quickly. The germ group excludes viruses, since they are not considered alive, although some people call viruses "germs" in everyday speech.

Benefits of germs

Some germs are beneficial in many ways: Yeast that make bread rise are germs. Oxygen we breathe is produced by microscopic algae. Fungi are used to make cheese, and different kinds of bacteria, known as probiotics, are used to make yogurt. Germs are also used to make medicines, and they even clean nuclear waste.

Some germs provide the human body with protein and important vitamins. Others crowd out harmful bacteria, or make acids that keep harmful bacteria from multiplying and making us sick.

Habitat

Most microbes grow best in moist and dark places. They stay away from too hot and too cold places.