Many bacteria are aerobic; that is, they require oxygen to grow and perform the biochemical reactions of their metabolism. There are, however, a large number of bacterial species that are anaerobic and are cultivated in a special apparatus where the oxygen has been removed. These bacteria (known as anaerobes) live in the absence of oxygen, and they are found in the muddy bottom of swamps, landfills, and soil. Some anaerobes are obligate anaerobes, while others are facultative anaerobes, meaning that they live with or without
oxygen.
