What term is used for bacteria that grow in the absence of atmospheric oxygen?

The term used for bacteria that grow in the absence of atmospheric oxygen is anaerobes. These organisms have adapted to thrive in environments devoid of oxygen, which can be found in various habitats such as deep soil, the gastrointestinal tract of animals, and other anaerobic environments.

Anaerobes can be further classified into two categories: obligate anaerobes, which cannot survive in the presence of oxygen, and facultative anaerobes, which can grow with or without oxygen but prefer aerobic conditions when available. This distinction highlights the adaptability of some bacteria to different oxygen levels, but obligate anaerobes represent those that rely exclusively on anaerobic metabolism.

In contrast, aerobes require oxygen for growth, while microaerophiles need low concentrations of oxygen. Thus, the identification of anaerobes as those capable of thriving in the absence of atmospheric oxygen is accurate, emphasizing their unique metabolic pathways that utilize compounds other than oxygen.