How big are Bacteria ?
All living things are made from tiny parts called cells. Bacteria are made from just one cell. They are the smallest living thing on Earth—so tiny that you can only see them with a microscope. Some bacteria are useful to us, while others make us sick.
Multiple shapes
Bacteria come in three shapes—rod-shaped, circular, or spiral. They reproduce by splitting themselves in half.
Microorganisms
This photo of bacteria was taken using a microscope. Microscopic living things are called microorganisms.
How tiny is microscopic ?
This yellow dot shows the size of bacterium compared to the thickness of a human hair. Twenty bacteria could fit in a row across one hair. Width of human hair is 0.003 in (0.1 mm) Width of bacterium is 0.0001 in (0.005 mm) The width of a bacterium compared to the width of a human hair
What other things are microscopic?
Viruses
Viruses are even smaller than bacteria. They live inside the cells of living things. When they reproduce they burst out of the cell, passing the virus on.
Fungi
Some fungi are microorganisms. Yeast is a single-celled fungus related to mushrooms. It eats sugar and releases gas. It is used in bread to make it rise.
True Or false?
1. Bacteria are used to make yogurt and cheese.
2. Bacteria come in four different shapes.
3. There are 10,000 bacteria on every 0.15 sq in (sq cm) of your skin.
