Obligate anaerobe

An anaerobic organism is any organism that does not require oxygen for growth. Obligate anaerobes will die when exposed to atmospheric levels of oxygen.Facultative anaerobes can use oxygen when it is present. Aerotolerant organisms can survive in the presence of oxygen, but they are anaerobic because they do not use oxygen as a terminal electron acceptor.
See more at Wikipedia.org...

Obligate anaerobe n. An organism, such as a bacterium, that can live only in the absence of oxygen. [more]Obligate anaerobe - Community and Resources

Noun
1. an organism that cannot grow in the presence of oxygen
(hypernym) anaerobe