Microaerobic incubation by commercial gas-generating envelopes in sealed jars. - Click on the image to enlarge it.
Microaerophilic bacteria require a reduced oxygen concentration for growth. They have optimal growth in 5-10% oxygen and some species are stimulted by 1-10% carbon dioxide. Bacteria that thrive in the precence of carbon dioxide are called capnophilic bacteria (or capnophiles).
The normal atmosphere consists of about 21% oxygen. This concentration is toxic for microaerophilic bacteria, which might lack efficient enzymes (catalase or peroxidase and superoxide dismutase) to detoxify hydrogen peroxide and superoxide radicals, which are produced when oxygen is dissolved in water (see anaerobic bacteria).
The growth of some species is enhanced by the presence of hydrogen, but the reason for this has not been clarified.
The cultivation of microaerophilic bacteria requires special laboratory technique. Several methods are used to generate microaerobic atmosphere. Microaerophilic bacteria could be culitivated in sealed jars or plastic bags with commercial gas-generating envelopes. Special incubators or sealed jars with valves for evacuation of the normal atmosphere and refilling of the optimal gas mixture can also be used.