anaërobia

from The Century Dictionary.

• noun The ability (on the part of bacteria) to live in the absence of free oxygen.
• A name given to bacteria which live without free oxygen, in distinction from aërobia (which see).

from the GNU version of the Collaborative International Dictionary of English.

• noun plural (Bacteriol.) 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.