Anaerobic Organism

An anaerobic organism or anaerobe is any organism that does not require oxygen for growth. It could possibly react negatively and may even die if oxygen is present. Most such species are unicellular microbes, though some are near-microscopic metazoa and some deep-sea worms. Some largely unicellular anaerobic microbes are protists, but most of the anaerobic microbes are bacteria or Archaea. For practical purposes there are three categories:

• obligate anaerobes, which cannot use oxygen for growth and are even harmed by it
• aerotolerant organisms, which cannot use oxygen for growth, but tolerate the presence of it
• facultative anaerobes, which can grow without oxygen but can utilize oxygen if it is present

In human beings these organisms are usually found in gastrointestinal tract.