Where Bacteria Are Found Bacteria are found in more varied habitats and environments than any other living thing. They are present on and within animals and plants. They exist in the ocean, on the desert, in hot springs, and in the snow of polar regions. Bacteria have been found many miles high in the atmosphere, at the bottom of rivers and lakes, and in the deepest mines. Some are able to flourish at temperatures high enough or low enough to kill other forms of life.
Most bacteria are smaller than yeasts, but all are larger than viruses.
A unit of length called a micrometer, or micron, is used to measure bacteria. It takes 1,000 microns to make up one millimeter and about 25,000 microns to make up one inch. Some bacteria are so small that their largest dimension is only one half a micron. Most bacteria range from 1 to 5 microns in size. The electron microscope, which can magnify more than 300,000 times, has greatly increased man's knowledge of bacteria.