Anaerobes

Organisms that do not require air or free oxygen for growth or maintaining life, and may even die in its presence. Those that grow only in the absence of oxygen are obligate, or strict, anaerobes. Some species, called facultative anaerobes, are able to grow either with or without free oxygen. Certain others, able to grow best in the presence of low amounts of oxygen, are called microaerophiles. Used especially in reference to microorganisms.