Nanaerobes are organisms that cannot grow in the presence of micromolar concentrations of oxygen, but can grow with and benefit from the presence of nanomolar concentrations of oxygen (e.g. ''
Bacteroides fragilis
''Bacteroides fragilis'' is an anaerobic, Gram-negative, pleomorphic to rod-shaped bacterium. It is part of the normal microbiota of the human colon and is generally commensal, but can cause infection if displaced into the bloodstream or surrou ...
'').
Like other
anaerobes, these organisms do not require oxygen for growth. This growth benefit requires the expression of an oxygen respiratory chain that is typically associated with
microaerophilic
A microaerophile is a microorganism that requires environments containing lower levels of dioxygen than that are present in the atmosphere (i.e. < 21% O2; typically 2–10% O2) for optimal growth.[ A more r ...]
respiration. Recent studies suggest that respiration in low concentrations of oxygen is an ancient process which predates the
emergence of oxygenic
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
.
References
{{Bacteria
Cellular respiration