Anaërobic bacteria. They are called facultative anaërobes when able to live either in the presence or absence of free oxygen; obligate anaërobes, or obligatory anaërobes, when they thrive only in its absence.

bacteria that can grow in the absence of oxygen

A group of organisms that do not require molecular oxygen. These organisms, as well as all known life forms, require oxygen. These organisms obtain their oxygen from inorganic ions such as nitrate or sulfate or from protein.

Anaerobic Anatomy The term anatomy refers to the internal structure of any biological entity. Plant anatomy studies the internal parts of the stem like the xylem, phloem, annual rings, fibers, etc. In animals, it is a study of their internal organs such as the stomach, liver, large intestine, gall bladder, etc.