What is the term for a bacterium that requires oxygen to survive?

An oxygen-dependent bacterium is called an obligate aerobe. It must have oxygen available for growth because it relies on aerobic respiration to release energy from nutrients, with oxygen serving as the terminal electron acceptor in its electron-transport chain.

This requirement distinguishes obligate aerobes from facultative anaerobes, which can grow with or without oxygen, and from obligate anaerobes, which are harmed by oxygen. Microaerophiles also require oxygen, but only at concentrations below normal atmospheric levels; too much oxygen can damage them.

In a laboratory thioglycollate-broth tube, obligate aerobes gather at the oxygen-rich surface. Examples include Mycobacterium tuberculosis, Bacillus species, and Nocardia asteroides. Their dependence on oxygen also creates a vulnerability: reactive oxygen compounds can cause oxidative stress, so aerobic cells generally need protective enzymes such as superoxide dismutase and catalase.

The word “obligate” means required, while “aerobe” refers to an organism associated with oxygen. Together, the term describes an oxygen requirement, not a particular shape, disease, or bacterial group.