Bacteria grow in a wide variety of habitats and conditions. When most people think of bacteria, they think of "disease-causing" organisms. While pathogenic bacteria are notorious for such diseases as cholera, tuberculosis and gonorrhoea, such disease-causing species are a comparatively tiny fraction of the bacteria as a whole.

Because bacteria are so widespread, it is only possible to make the most general statements about their life history and ecology. Bacteria may be found on the tops of mountains, the bottom of the deepest oceans, in the guts of animals and even in the frozen rocks and ice of Antarctica. They have the ability to go dormant for an extended period of time which is a factor that has enabled them to spread so far and last so long.

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