The Methylococcaceae are a family of
bacteria
Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among ...
that obtain their
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
and energy from
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Eart ...
, called
methanotroph
Methanotrophs (sometimes called methanophiles) are prokaryotes that metabolize methane as their source of carbon and chemical energy. They are bacteria or archaea, can grow aerobically or anaerobically, and require single-carbon compounds to su ...
s.
[.]
They comprise the type I methanotrophs, in contrast to the
Methylocystaceae
The Methylocystaceae are a family of bacteria that are capable of obtaining carbon and energy from methane. Such bacteria are called methanotrophs, and in particular the Methylocystaceae comprise the type II methanotrophs, which are structurally ...
or type II methanotrophs. They belong to
Gammaproteobacteria
Gammaproteobacteria is a class of bacteria in the phylum Pseudomonadota (synonym Proteobacteria). It contains about 250 genera, which makes it the most genera-rich taxon of the Prokaryotes. Several medically, ecologically, and scientifically imp ...
, and are typically given their own
order.
The Methylococcaceae have internal membranes in the form of flattened discs, perpendicular to the
cell wall
A cell wall is a structural layer surrounding some types of cells, just outside the cell membrane. It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mech ...
.
Methane is oxidized to give
formaldehyde
Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
, which is fixed by a process called the
ribulose monophosphate (RuMP) cycle. Here
formaldehyde
Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...
is combined with sugar
ribulose
Ribulose is a ketopentose — a monosaccharide containing five carbon atoms, and including a ketone functional group. It has chemical formula . Two enantiomers are possible, -ribulose (-erythro-pentulose) and -ribulose (-erythro-pentulose). ...
, producing
hexulose
In chemistry, a hexose is a monosaccharide (simple sugar) with six carbon atoms. The chemical formula for all hexoses is C6H12O6, and their molecular weight is 180.156 g/mol.
Hexoses exist in two forms, open-chain or cyclic, that easily convert ...
. This, in turn, is broken down to produce
glyceraldehyde
Glyceraldehyde (glyceral) is a triose monosaccharide with chemical formula C3 H6 O3. It is the simplest of all common aldoses. It is a sweet, colorless, crystalline solid that is an intermediate compound in carbohydrate metabolism. The word comes ...
, which is used to produce new ribulose and other organic compounds.
Catabolism
Catabolism () is the set of metabolic pathways that breaks down molecules into smaller units that are either oxidized to release energy or used in other anabolic reactions. Catabolism breaks down large molecules (such as polysaccharides, lipids, ...
does not involve a complete
citric acid cycle
The citric acid cycle (CAC)—also known as the Krebs cycle or the TCA cycle (tricarboxylic acid cycle)—is a series of chemical reactions to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins ...
.
[George M. Garrity: '']Bergey's Manual of Systematic Bacteriology
''Bergey's Manual of Systematic Bacteriology'' is the main resource for determining the identity of prokaryotic organisms, emphasizing bacterial species, using every characterizing aspect.
The manual was published subsequent to the ''Bergey's Manu ...
''. 2. Auflage. Springer, New York, 2005, Volume 2: ''The Proteobacteria, Part B: The Gammaproteobacteria''
Some species of the Methylococcaceae have formed with certain marine mussels endosymbiotic relationships.
References
External links
MethylococcaceaeJ.P. Euzéby: List of Prokaryotic names with Standing in Nomenclature
Gammaproteobacteria
{{gammaproteobacteria-stub