A microaerophile is a

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

that requires environments containing lower levels of

dioxygen There are several known allotropes of oxygen. The most familiar is molecular oxygen (), present at significant levels in Earth's atmosphere and also known as dioxygen or triplet oxygen. Another is the highly reactive ozone (). Others are: * Ato ...

than that are present in the

atmosphere An atmosphere () is a layer of gases that envelop an astronomical object, held in place by the gravity of the object. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A stellar atmosph ...

(i.e. < 21% O₂; typically 2–10% O₂) for optimal growth. A more restrictive interpretation requires the microorganism to be obligate in this requirement. Many microaerophiles are also capnophiles, requiring an elevated concentration of

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

(e.g. 10% CO₂ in the case of '' Campylobacter''

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

). The original definition of a ''microaerophile'' has been criticized for being too restrictive and not accurate enough compared to similar categories. The broader term microaerobe has been coined to describe microbes ''able'' to respire oxygen "within microoxic environments by using high-affinity terminal oxidase".

Culture

Microaerophiles are traditionally cultivated in candle jars. Candle jars are containers into which a lit

candle A candle is an ignitable candle wick, wick embedded in wax, or another flammable solid substance such as tallow, that provides light, and in some cases, a Aroma compound, fragrance. A candle can also provide heat or a method of keeping time. ...

is introduced before sealing the container's airtight lid. The candle's flame burns until extinguished by oxygen deprivation, creating a carbon dioxide-rich, oxygen-poor atmosphere. Newer oxystat bioreactor methods allow for more precise control of gas levels in the microaerobic environment, using a probe to measure the oxygen concentration or redox potential in real time. Ways to control oxygen intake include gas-generating packs and gas exchange. As oxystat bioreactors are expensive to buy and run, lower-cost solutions have been devised. For example, the Micro-Oxygenated Culture Device (MOCD) is a system involving ordinary flasks, oxygen-permeable tubes, sensors, and water pumps. Aeration is done by pumping the culture medium through the tubes.

Examples

A wide variety of microaerobic conditions exist in the world: in human bodies, underwater, etc. Many bacteria from these sources are microaerobes, some of which are also microaerophiles. * Some members of Campylobacterales are microaerophilic: ** '' Campylobacter'' species are microaerophilic. ** ''

Helicobacter pylori ''Helicobacter pylori'', previously known as ''Campylobacter pylori'', is a gram-negative, Flagellum#bacterial, flagellated, Bacterial cellular morphologies#Helical, helical bacterium. Mutants can have a rod or curved rod shape that exhibits l ...

'' (previously identified as a ''Campylobacter''), a species of Campylobacterota that has been linked to

peptic ulcer Peptic ulcer disease is when the inner part of the stomach's gastric mucosa (lining of the stomach), the first part of the small intestine, or sometimes the lower esophagus, gets damaged. An ulcer in the stomach is called a gastric ulcer, while ...

s and some types of

gastritis Gastritis is the inflammation of the lining of the stomach. It may occur as a short episode or may be of a long duration. There may be no symptoms but, when symptoms are present, the most common is upper abdominal pain (see dyspepsia). Othe ...

* Many members of ''

Lactobacillus ''Lactobacillus'' is a genus of gram-positive, aerotolerant anaerobes or microaerophilic, rod-shaped, non-spore-forming bacteria. Until 2020, the genus ''Lactobacillus'' comprised over 260 phylogenetically, ecologically, and metabolically div ...

'' sensu lato (see

Lactobacillaceae The ''Lactobacillaceae'' are a family of lactic acid bacteria. It is the only family in the lactic acid bacteria which includes homofermentative and heterofermentative organisms; in the ''Lactobacillaceae,'' the pathway used for hexose fermentati ...

) are microaerophiles. As facultative anaerobes, they do survive anaerobic conditions, but grow better with a little oxygen. * '' Magnetospirillum gryphiswaldense'' and '' Magnetospira'' sp. QH-2 are aquatic microaerophilic

magnetotactic bacteria Magnetotactic bacteria (or MTB) are a polyphyletic group of bacteria that orient themselves along the magnetic field lines of Earth's magnetic field. Discovered in 1963 by Salvatore Bellini and rediscovered in 1975 by Richard Blakemore, this alig ...

. The formation of magnetite in such bacteria in general require microaerobic conditions.

References

External links

Characterization of an unclassified microaerophilic bacterium associated with gastroenteritis.
Microbial growth and nutrition {{Microbiology-stub

Culture

Examples

See also

References

External links