Are bacteria really everywhere?
(Lansing State Journal, October 5, 1994)
Tiny forms of life have adapted to a whole spectrum of environments. But it is important to keep in mind that not every microorganism can live in every environment. There are different species of plants and animals. The bacteria that live in the rocky tundra aren't the same as those that live in hot springs.
Any place that offers the basic nutrients required for life will almost always have microbes. "Almost always" because changes in local environments may make that place sterile. For example, when we cook food, we may end up killing all the microbes that may be on or in the food. When it cools on our plates, it could support more living bacteria, but none may land on it for a while. For a short time, that environment does not have any living bacteria on it. Eventually, though, if a place can support life, it will at some point. And generally, the first forms of life to live and grow there will be microscopic.