Anaeroobe

Anaeroobe is a term used to describe organisms that do not require oxygen for growth and may be harmed by exposure to oxygen. In microbiology, anaerobes are often contrasted with aerobes, which require oxygen for metabolism. Within the anaerobes, there are several subgroups, including obligate (strict) anaerobes that cannot tolerate oxygen, and facultative anaerobes that can grow in the presence or absence of oxygen by switching between aerobic respiration and anaerobic metabolism. There are also aerotolerant anaerobes that do not use oxygen but can survive in its presence.

The metabolism of anaerobes typically relies on fermentation or anaerobic respiration, using alternative electron acceptors rather than molecular oxygen. Many anaerobes lack or have very limited activity of enzymes that detoxify reactive oxygen species, such as superoxide dismutase and catalase, which makes oxygen harmful to them. As a result, oxygen-rich environments can inhibit or kill obligate anaerobes, while some facultative and aerotolerant anaerobes are more tolerant of oxygen.

Anaerobes inhabit diverse environments where oxygen is scarce or absent. They are common in deep soils, sediments, swamps, and the gastrointestinal tracts of animals, including humans. In the human gut, anaerobes contribute to digestion and vitamin production, while some species can be pathogenic under certain conditions, such as Clostridium difficile or Clostridium perfringens. In industry, anaerobic processes are exploited in fermentation and the production of certain chemicals.

Cultivating anaerobes in the laboratory requires removing or reducing oxygen, using specialized media with reducing agents, anaerobic jars or chambers, and gas packs. This ensures an environment suitable for growth and study.